Banning them would be a little bit too harsh IMO, but reviewing each of those posters for a signature ban would be completely fair.
I think it's a great punishment for low-quality posters, it immediately hits them where it hurts.

Btw, I'm talking about a temporary sig ban, like mentioned in the OP, 30 days should do the trick.
They'll either give up or change their ways, in any case it sends a really strong message to would-be-spammers.