Right, so you are referring to campaign managers not accepting multi accounts? Well, most of the Bitcointalk ones do, and I think some bounties specify that its against the rules to have more than one account enrolled owned by the same user. But, it's hard to enforce, and prove. I would wager there are several accounts that are owned by the same person in the same campaign, even the Bitcoin ones. In fact this has been proven to be right in the past.

Implementing restrictions on certain ranks not having signatures would tackle this issue, though. Simply restricting multiple accounts either through campaign managers or through the forum rules isn't going to be effective even if we throw out the perfectly legitimate reasons to have an alternate account. It's simply to hard to prove. At the moment the people with hundreds of accounts probably only use a VPN, and likely don't try, and hide their information all that well. But, if we were to impose hard limits they would soon find a way around it by using VPNs/Tor, and different addresses for their multiple accounts. They might even go so in depth that they look at timing analysis or changing the national spellings of certain words between their accounts.

Could be an interesting solution to the issue. Although, this is something that would have to be adopted by bounty managers, and most of them don't actually care about the spam issue. All they care about is their advertisement, and hype around their project.

Theymos could potentially come out with a set of guidelines which bounty managers have to follow otherwise their thread will be removed. This could be an approach which would avoid too many official restrictions, but would deal with some of the issues. Whether, the forum has enough users reporting, and the manpower to enforce this though is another thing.