At one point I had over 2000 friends. Playing the games sucked me in bad. Each game required you having 500 friends to play if you wanted to be competitive. I got smart later and joined groups where people played more than 1 game so cut down on how many friends I really "needed."
Over time I stopped playing this game, that game and this other game(s) that was pulled from FB (not enough $$ coming in from it/them). So I had hundreds of friends that I had nothing but a game in common with that we no longer played (cos some of those friends quit playing some of their games too).
When I got down to the 2 games that I can see myself paying .. err playing for the next umpteen years or until FB implodes.. I did one of those Events where you invite your entire friend list. I said pretty much what the OP said was posted but with mention of the 2 games I play and people could keep me if they found me enthralling ;-)
People still active in playing game A, B or C could then drop me with no hard feelings, freeing up their friend list to people playing the games they played. Making room to add more people for that game as well.
People who actually got to know me kept me. People who just added me to have their 501 and then had hid me from view (to keep their newsfeed showing real friends vs game friends) deleted me.
The other 1500 either play the same games as me, are related, are real life friends or didn't care to check out the Event. Slowly I have been going person by person and deleting them. People who no longer play "my" games, people who haven't been on FB for years, people who lost access to their accounts.. whatever. It would have been easier if they had attended the Event and just unfriended me if they could but.. now I have to do it.
Just in case some other game comes along that needs me to have 500 players and maybe a game after that
The 5000 friend limit means culling. Throw in the new algorithm FB uses to decide just whose posts you can (instead of letting me see what everyone is posting). Oh and how having more than a 1000 friends can mess up some games (the gifts etc).
Now just posting that to see some sort of validation would be tacky. Right up there with the slacktavist "if you cared about ... you would repost this. How many of my friends will care." type of posts. But to maximize culling.. not a problem.