Perhaps unlimited alts in each IP address (so schools, clubs, or wifi access points can play), but accounts that enter through the same ip cannot attack the same things. Like, camps, outposts, bases, enemy player bases, and maybe even bases inside alliances of others on the same IP. It would help deter both multi-player gaming and some locking out during attacks.
@gamerdruid don't sweat the attack from Furyanmonk. He has been kicked from alliances before due to saying not-intelligently-concieved ideas in an obnoxious way. He is a hater at heart. At least it seems he has his Tourette's Syndrome somewhat under control, and we can all be happy about that. :) He can be a lot worse.