I think soon bounties will die, because now most projects that holding bounty it's scam. Already I see less bounty campaigns and with time will be lower.
It belongs to the signature campaigns, I also do not think it works well. Signature campaigns are useful for introducing existing projects. In addition, I do not think the whole bounty is worthless. Every project needs marketing, even if not here, in other places. For marketing it is more accurate to choose where the crypto community is most gathered, and bitcointalk is optimal to these indicators. Projects can not find any better place to announce itself.