podge wrote:multies get busted
secret alliances get blocked
I think

Well thats true. Secret alliances are the gray area since they are very hard to prove. Similarly if there is a case that looks like the players are multis but I'm not convinced of it I will often just block them as a precaution. It's a nice middle ground.
That especially applies in cases with a premium member who might have multis but its not clear. A premium would have no purpose in taking turns for extra accounts if they can't play together (unless its some sort of personal challenge). Freemium members on the other hand sometimes make multi accounts just to play more games (and not boost their score). It's still cheating, and blocking the accounts from playing together doesn't solve the problem but its better than nothing.