Thread bumping/spamming is starting to look like an industry, earning thousands of dollars per month! Bitcointalk should end this, maybe reject all Newbies and if needed Jr. Members too from those boards?
Or, as I suggested elsewhere: sell sticky spots for spam-free campaigns on those boards. If they're willing to pay 0.42BTC per month to be on top, let them pay it to the forum.
Another tactic would be to temp-ban the OP of the thread on the presumption they paid for the service. That is a bit more heavy-handed, I'll admit, so a lesser penalty would be "The Scarlet Letter" approach: temporarily lock the thread with a notice that it was done because of paid thread-bumping. The bad PR from that should vastly outweigh whatever (questionable) benefit might be derived from keeping a shitcoin's thread on the first page.