Probably 6-8. Some are usernames that I make with the desire that no one could link them to me in any way. Like my twitter account. Because I know that clients will eventually google search my name and I would rather tell them who I am in person then rely on interpretations of my online behavior (which is so easy to misinterpret).
6-8 easily, but I can only remember about four.
... Wow. I just looked up my first username, which linked me to some rather embarrassing attempts at humorous fiction I wrote eleven years ago. Glad I checked before I shared that name. Scary that it's the first hit for a rather common phrase.
Just two- my first username which I used to use just about everywhere (including Giantbomb) was just my first name with a bunch of numbers. I was a total 'noob.' I changed it in 2008 to this one, though. I like it better, but if you did back deep enough, there's definitely some stuff I said when I was 18 that I'm ashamed or embarrassed about now. I've considered coming up with a new online persona for a fresh start, but I don't think it'd be worth it.
3 in total.. I have two right now (fucking Xbox live god damn stupid shit not letting me get my other account back)
Now I mostly just use my real name as a username when I get the chance.
Sure people can then look me up on facebook and see all my dirty little secrets.
Like, I kiss girls and I have fun at parties. Oh also, I drive a car.. oooh, what dangerous things people will know!
2 or 3
One when I was younger, still use the email address with that one, but nothing else really.
GB username, which I think I only use here, and only because I thought the one I originally tried was taken, but it wasn't.
For everything else, for the past 5 or 6 years has been FuzzyLongcat, or Fuzzy if available