I don't think it's a huge issue if these campaigns move their management off-site. If we start banning campaigns and their participants which are largely spamming, future campaigns will very quickly learn to employ a manager who actually pays attention to post quality.
IMO Stake campaign was sufficiently bad but it didn't get the same treatment as Yobit, and its manager and participants didn't seem to be concerned about the spam or the Yobit precedent. Not every such campaign is going to have someone like Stunna to pull the plug. So I'm not certain if it's a good deterrent to ban a URL and everyone carrying it when some unknown arbitrary spam threshold is breached. Shitty offsite campaigns would just roll the dice (pun intended) - it's mostly their participants at risk anyway, not the "management".