In single-player don't starve, beefalo extinction was a mechanic that made sense, If the player was foolish enough to hunt beefalo to extinction, they would have to put up with not having any more beefalo.
In multi-player, I don't think it makes as much sense, The actions of one incompetent hunter can punish every player on the server by removing a useful resource forever. Sure, you could spawn in beefalo, but cheating is for wankers.
So I propose this: Stray beefalo!
Perhaps when beefalo are completely extinct, you'll have a chance to find a stray beefalo instead of a koalefant at the end of a trail. This way you'll always be able to recover from a potential extinction.