Damon as a Scorpio

When I first opened Scorpio Boy, the title was very much a whim. We did not know the sun signs of the characters and it was up to fans to decide what they thought fit best. When LJS retuned to fandom, I sent her a letter asking her whether I - and many other fans - was right, was Damon a scorpio? She replied:
...sort of spooky actually. Damon, of course, would have to be born on Hallowe'en--midnight of the 30th actually. Which would make him a Scorpio, I believe. ...Do [fans] also assume that Stefan is a Virgo, or do they just not give a...darn?
The following is a bit of information about the sign Scorpio, and how well Damon fits.

The Basics

Scorpios are born between October 23 and November 21, the eighth house in the zodiac. Each house in the Zodiac has a God/Goddess attributed to it, and Scorpio is 'ruled' by Pluto (Roman God of the Underworld) and Mars (Roman God of War). Scorpio's are a water sign, which implies some degree of emotional connection for these people in anything that they do. The symbol of this sign is that of the Scorpion; an animal that seems harmless, but can give you a nasty sting if you push it the wrong way.
The chief characteristics of Scorpio's are energy and jealousy, they are often seen as the 'worst' sun sign, but most astrologers believe this is simply because their emotions are often strong and over-powering. Resourceful and fearless, they are however, driven by their emotions to the extent that they can become over-powering.

Emotions

Scorpio's are described as one of the most powerful and intense star-signs, they can maintain a calm and collected exterior in the face of their anger. Scorpio’s have a tendency to go to extremes in their actions, but also in what they like and dislike. Scorpions can lose their temper (and even become vengeful) when someone gets in their way, they're unafraid, and a loss today simply means an opportunity for victory tomorrow, they also are not above a little manipulation to make sure they have their own way. Scorpio's are concerned with beginnings and endings, and are unafraid of either; they also travel in a world, which is black and white and has little use for gray. However, despite a tough exterior, they are ruled by the element water, meaning they are emotional people, and their emotions can often rule their actions and reactions to different situations. Unlike the other water signs (Cancer and Pisces), they are more likely to keep this under wraps. A good description of Scorpio is the old adage; still waters run deep;. They will not let on their inner emotions, but if they are annoyed they are likely to strike out with vindictiveness; returning to their composed self after doing so, but keeping a record of the fact that you crossed them.

Damon? Throughout the books Damon rarely gives away what he is really thinking. However, on two key occasions he snaps, but then gathers himself together before he lets too much slip; such as in VD3 when Elena bugs him to go and help the town, and in VD4 when Stefan is taunting him to react when he lets Klaus kill Vicki. Damon, like a typical Scorpio, is ruled by instinct and emotion, but he doesn’t; allow that; to be too obvious. He lets his desires and anger lead him into action, but never lets anyone really get under his skin. Elena seems to be the only person that finds what’s under there- as is shown in VD3 when she is dying. Of course, for another example, there is the famous scene at the end of VD4 when Damon threatens Klaus when he is trying to kill him.

Driven

Although they will not show it, Scorpio's are driven by their emotions. This often leads to the appearance of the darker; qualities which Scorpio's are notorious for - resentment, aggressiveness and sadistic brutality, arrogance, jealousy and extreme volatility of temperament. At the other extreme is the procrastinator, the man or woman who is capable of so much that they do nothing and become indolent and self-indulgent, requiring extravagant praise and flattery from those whom they make their 'cronies'.
But this should not drag down their sign, because when they are motivated, they are aware and penetrating. They don’t miss much in the way of what is going on around them; they are intuitive, probing and very focused on knowing who's who and what's what.
Wilful and passionate with whatever gets their emotions going, they can be critical of what they dislike, meaning they make; enemies easily. However, they can also harness their abundant energy constructively, tempering their self-confidence with shrewdness and their ambition with nobility toward others provided they like them. They relate to fellow workers only as leaders and can be blunt to those they dislike to the point of cruelty. In fact they are not above expressing their vindictiveness in deliberate cruelty.

Damon? While the above comments are broad and to the extreme, Damon is portrayed as an aggressive, brutal and arrogant character. He plays up these attributes to get reactions from other characters, in particular Stefan and Matt.
In one of Stefan's flashbacks, we see an argument between Damon and his father, where Damon flaunts that he is not going to return University, that he intends to enjoy himself. But despite this apparent laziness, Damon shows that when he wants something (such as Katherine or Elena) he will use all of his means - charm, ambition - to achieve what he wants.
During the book, we see that Damon can use his power to be cruel - often to teach someone a lesson - that they should not cross him. Damon uses his power against both Stefan and Elena when he is angered by them and threatens others.

Relationships

Scorpio is the symbol of sex, being one of the more passionate signs in the Zodiac. Those under this sign can 'soften up' when in love, showing their more caring and devoted side. But their sensitivity, together with a propensity for extreme likes and dislikes make them easily hurt, quick to detect insult or injury to themselves (often when none is intended) and easily aroused to ferocious anger.
The area of the body ruled by the Scorpio is the genitals, which explains the reputation of Scorpio being the 'sexiest' sun-sign. They feel attraction and love acutely, and if they find something that they want can put a lot of time into getting it. Their energy also comes into play during courtship. They can often channel their efforts into the 'hunt' enjoying the chase so much that they can pursue what they want, even when they know the person isn't the right one for them.
Scorpios need a partner that can help them channel their energy, someone who can be there to support them. Scorpions do, however, make excellent friends, provided that their companions do nothing to challenge the honor of which Scorpios are very jealous. Along with jealousy, part of the negative side of the Scorpio nature is a tendency to discard friends once they cease to be useful, but the decent native is aware of, and fights this tendency.

Damon? It is clear from reading The Vampire Diaries that Damon was portrayed as the sexy elder brother, Stefan often 'laments' at women being drawn to his brother because of his charm.
Damon also, savors the 'chase' and uses all of his energy to try and attract Elena and Katherine. Even when it was clear that Elena was in love with Stefan, Damon did not relent.
Jealousy is also a key fault of Damon, who often is very possessive and wants something just for wanting it. For instance, at the beginning of VD3 when Damon walks in on Stefan and Elena embracing in the church.

Competition

Scorpios love competition in both work and play, extreme sports are right up the Scorpion's alley, as is most anything, which will test their mettle. Scorpio's enjoy things that push them, enjoying the thrill of danger. They've got to have an adversary, since it makes the game that much more fun. Scorpios work as hard as they do so they can someday sit back and feel satisfied with themselves. These people are intense, passionate and filled with desire. They're also complex and secretive, so don't expect to get much out of them, lest they become suspicious and exit stage left. It's best not to bet against Scorpios, either, since these folks are surprisingly resourceful.

Damon? Damon enjoys the competitive relationship between Stefan and himself. As has been mentioned in other section, Damon continues to push his brother into corners he would rather not be in. Damon tries to elicit a reaction from Stefan and taunts him until he snaps.

The Scorpion's colors?

Powerful red and serious black.

Overall

The great strength of the Scorpio-born is in their determination, passion and motivation. Scorpions don't know the word quit, which is why they usually get the job done. A powerhouse? Like no other.