I like Facebook. I'm not a big user of it, and think they could change "Friends" to "Acquaintances" to be more realistic in most cases, but it must be great for kids to grow up and never lose touch with people they meet.
My age/era means that many people I'd rather like to catch up with are lost forever.
Many people spend their entire lives moving from place to place, country to country, I like the way FB allows you to maintain a virtual village of acquaintances. You can interact or not, it's your choice.
I have received many requests from what I call "Friend collectors" though, people I've met through other people but have only the slightest recollection of. I think my friends list is pared down to people I've at least had a pint with.
If you can't remember their last name then delete them.