On my new account, this has only happened twice, but my old account... Yesh, too, too many times. On this account, I want it look neat, so I don't really accept friend requests unless I've talked to that person for more than a little over an hour.
I just don't like my friend's list cluttering up until I don't see anyone anymore and risk my game possibly glitching horribly wrong (like, game-breaking glitches).
However, I do feel noticed and liked whenever I get friend requests, even if it is random or a mistake, and that helps slightly boost my self-esteem, I suppose. I just never accept them because, for all I know, they could be someone completely the opposite of what I find likeable in a person (personality wise, of course).
-Wolfie