I do care enough about my friends list to keep it trim; usually once a month or so.
I pretty much outline it right on my profile that I don't like random requests, and I don't feel bad in doing so. It never hurts to drop me a VM/PM or two and try to strike up a conversation before asking. Usually, if I've talked to you and I like you, I'll be willing to add you. I do enjoy making friends, but I'm not going to add just anybody to my list.
I don't typically drop people for arbitrary reasons though, only if I haven't heard from in a long time and can see they've left PC