I'm leaping back onto the not-a-meme bandwagon and answering the most recent question...
Do you consider your avatar an extension of yourself, or a character you can control? (question posed by Jacek)
I am Coal, Coal is me. There are some pointed differences (in SL you never have a bad hair day or discover that a mini-marshmallow you accidentally dropped next to the laptop has melted and become one with your favourite pajama pants), but overall, I see Coal as an extension of me. I don't, in fact, have antennae in real life (although I am fortunate enough to have several good friends whose brains I occasionally time-share).
Coal was my name in several other online communities before SL and my nickname within my family since pretty much the day I was born (my cousin couldn't say my real name). I've never really had another nickname that I answered to. Except Coalie, which really doesn't count.
She talks like me and the opinions expressed tend to be those held by the RL person. :D I type like I talk, really. In some ways more eloquently (thank you Mr. Backspace), but over the years my writing has become very stream-of-consciousness. Coal behaves in the ways that I behave in RL - except that I have more patience for shopping in SL (no doubt because everything fits there and you don't get in the dressing room only to discover you've got entirely the wrong size/colour/cut/material/store) and have never line-danced (or wanted to).
Coal wears clothes that in general match my taste (granted, hers can be a little more risque because they don't tend to be affected by things like gravity, laundering, stains, propriety, or making-my-butt-look-fat).
Coal's hairdo changes colours, but is pretty close to mine in the cut (I am always on the lookout for something closer). In fact, I was thinking about cutting my hair (offline, I mean) and tried on a variety of hairdos (in-world) to see what they would look like.
I have a couple of alts. The first one I created to figure out how group stuff worked... and it got kind of fun to play with. So now if I'm bored and see an interesting new last name go by, I create an alt. If you're honest, it costs you a one-time-fee of $10. If you're not honest and say it's your first account, it's free, but frankly... I'd rather buy an alt than go see a movie, so I pay. I was also a Girl Guide when I was a kid. :P
The odd thing is, I've found that the longer I'm logged in as the alt, the more they will start looking like Coal. Or like me. It's kind of creepy. But I feel like a git wandering around all ruthed, and a few stabs at the sliders, and some prim hair later... the avatar starts looking like Coal's overly-made-up sister. Or whatever.
I don't think I consciously chose to make Coal look like me. The evolution has been an ongoing process - she's not there yet, and there are certain things about the RL me I doubt I'll ever incorporate into Coal (and vice-versa) but figuring out how to work the sliders to make her chin look like mine has been fun (for some definition of 'fun').