I was trying to see how many friend requests I could accumulate but I heard that lots of them could cause lag so I cut mine down to people I know through forums or know in game. I also heard that being in a big guild increases lag. I suggest setting it up so that friend requests automatically delete after a week. If you set it up to where you could only have 1000 friend requests and then can't recieve any more after that then you may not be able to recieve one from someone you actually want to be friends with (although you could just decline a few to free some slots up). I would think a friends list of 500 would be big enough for anyone but some people may want more. I'm not sure what you can do about guild size though...