...
It's an insane incentive, and indeed, it would be good if the forum limits access to those boards to higher ranks only. But if that happens, they'll start spamming other boards to gain activity. Letting them spam the bounty boards is the lesser evil choice.
There's no use if they gain activity as long as they don't have the merits needed to rank up...
Maybe we can split the forum to bitcoin and altcoin section (as TheQuin has
mentioned already)
The bounty hunters won't have access to bitcoin section, so they could only destroy the altcoin section but bitcoin will survive...