Sure,

Bounties discourage collaboration, as devs are 'competing' for the bounty vs working together. I don't want to compete, I want to collaborate. Bounties put pressure on to develop as fast as possible just to claim the bounty. Bounties don't provide an incentive to continue a project once they're claimed. Bounties are vague and there is a very high chance of not satisfying the 'requirements' that are loosely defined.

Most bounties that are successful are small feature requests on existing software and usually completed by the author of the project.