What happens to these people is you never respond to their friend request because you don't want to be their friend and you don't want them to either 1) know you declined them or 2) be able to request you again. They then spend the remainder of their life pending, while you hope they assume you have a buildup of requests that you generally don't respond to.
2) I like posting my drinking stories on my status all the time; so sorry Mom, you're pending for life!
3) Alex: Yo Ben, isn't this that bitch I said 'hi' to last week who ended up puking all over Evan's new couch like 30 minutes later?
Ben: Ya I think so, why the hell is she adding you on Facebook?
Alex: I don't know bro, I never thought she would be able to remember me, she is for sure pending for life.