I also think that we need to be harsher on campaign managers to enforce their rules more strictly and have stricter rules about spam. I think that punishing managers for their campaigners' spammy behavior would be a good incentive to get them to be stricter. Perhaps giving out bans to managers if their campaigners are being spammy and nothing is done about them after they are informed of spammers.
Unfortunately, one of the most notorious signature campaigns, (the one I am currently involved in at the moment,) has the help of a Global Moderator, and it is still heavily abused. Poor guy has to keep playing wack-a-mole and have hundreds of accounts banned from the campaign, and the spammers still crop up like so many weeds.
With my short experience with the current signature campaign, I must admit, the temptation to post absolute crap definitely keeps nagging. Overall, it has been a good experience for me because it has actually made me expand my reading outside of the altcoins announcement forum. I have actually leaned quite a bit. Unfortunately, I think most in the sig campaigns do not actually take much time reading the content of the thread before posting.