And I say it both as a contributor, but also a consumer. Sometimes I'd be happy to throw $100 on top of some specific issue of a lib/app I use regularly to incentivize its resolution.
I wish this service didn't require repo owners to do anything before they see some actual bounty assigned to one of the issues. So, theoretically, I could go and assign a bounty to any repo on Github right now, and the owner (and maybe the public) would see it right away.