It's so much like that. You have to manage it. It took me a while to learn how. (And note that i am not there with my real name.) Managing it became a lot easier in last 6 months or so.
When you get friend requests from people you don't know, you can ignore them, or accept them and when you see (usually almost immediately) that they feed out crap, you either remove them or you (more recent feature) unsubscribe from them. When you unsubscribe from them, they stay on your friend list but you pretty much forget they're there because you never see their stuff on your 'newsfeed'.
fb "applications"... NO. I learnt that. Aside from them being mostly childish, there were too many cases of friends saying their "accounts had been hacked" and if their friends got dirty stuff from them, that was how, it wasn't actually them. So, no applications, ever. Just ignore. Simple. Don't do it.
total strangers informing you they had hit you in the face with a custard-filled water pistol etc
"Applications"...first, why did you have total strangers in the first place? Then, as soon as you see some "friend"
does that stuff, delete them.
DELETE and BLOCK.
None of that happens to me anymore - although i didn't get that much of it to begin with.