Some Quick Ideas

iSeeBOOT^t

I have a huge friends list, I've tried unfriended most inactive people and everything but it seems endless, so maybe they can add a feature where if a player hasn't been active for a good week or so a message could pop up asking if you would like to unfriend them. It doesn't sound the best in writing but, just an idea.
Another idea which includes friends list is a friend bumper...
Works just like a food warp but instead teleports to a certain friend on your friend list. I dunno these seem a little bit odd but just ideas man.

Pizza Steve

We already have this, in a way... Players are categorized in your friends list in order of who's been online most recently. You could just scroll down the list and unfriend whoever's been the least active.

Warp food for friends i'm unsure of, since you could more or less acheive the same result by warping to them from the friends list. Seems like a waste of effort.

The friends list could be better, though. I'd wager a system for "Best Friends" could be added to help you find your best buds quicker.