Good to know that you report against spammers. Actually we all are facing this problem to some extent. I have posted a message about the same issue.
I think we (freelancers) can rduce the number of spammers by flagging and reporting. We need to be aware about this. Newbies are more vulnerable to the spammers.
So warnings can be sent to both new freelancers and clients when they open new account just like we see when a client is using template for posting jobs.
Finally its up to oDesk and they can be more cautious and strict on clients accounts.