LJ-Friends Policy: I recognize the disconnect between LJ-friends and real-life friends. While there is significant overlap, a member of one group is not guaranteed to be in the other. I recommend a similar viewpoint for all LJ users, really.
As a courtesy, I friend anyone who friends me, but I read my friends page through a private filter that displays only those writers whom I find actually interesting, and make secure posts to another private filter that more or less fits the definition "people I know in non-LJ contexts, who are not insane".
I may decline to reciprocate LJ-friend-ness to anyone who looks like a troll, spammer, or astroturfer, or to real people whose writing I find actively saddening for whatever reason (as opposed to merely uninteresting).
Occasionally, I will friend people I don't actually know, if I happen to stumble across their LJs (usually through "friendsfriends" or comments left on mutual friends' posts) and find their writing interesting. If this has happened to you: hello! I find your writing interesting, apparently. You can friend me back, or not, at your leisure. It's all good.