If all managers required Bitcoin for signature campaign payment via escrow, then I think spam and scam both will be reduce.
I wholeheartedly agree with this suggestion, as I've seen a few campaigns/bounties/whatever scam their participants by not escrowing the funds for same. There's really no reason not to, and no reason why the project developers can't hire a good campaign manager and have things run right. People should treat any bounty/campaign that hasn't escrowed funds with extreme skepticism and think twice about joining it.
As far as
requiring this, I don't think that's something Theymos is looking to enforce. There have been a lot of really good suggestions about how to decrease spam and to keep ICO projects in line, but they've apparently fallen on deaf ears. You do realize that scams aren't even moderated here, right?