Isn't the feedback left by yahoo sufficient enough?
Correct me if I'm wrong, but I don't recall a flag being opened against multi-accounts so far. It's too much imo.
edit;
It's not about multi-account it's about the cheating attempt.
I meant multi-accounts as in 'multi-accounting' meaning cheating bounties/sigs with alts. Still, i believe flags should be reserved primarily for scammers and the tag left by yahoo is a pretty significant warning by itself.