I've read that bounties on questions move the question to the featured questions. I think this is a complete waste, bounties and featured questions should be made separate. If a bounty is not awarded the system should ask the person who made the bounty if they would like to keep the bounty available indefinitely (or until they run out of the reputation to keep the bounty in place) or not. Paying reputation for the featured questions tab which is not refunded is fine, that truly is taking up a spotlight. I don't care if an important question I have is featured, otherwise I would create a much higher bounty.
The problem is bounty periods do not account for more obscure subjects/topics/languages/etc and even if the s/t/l is not obscure people have a tendency to post generic answers to questions, not testing code if code is involved, etc. In example if I place a bounty on an Apache related question I wouldn't mind having it awarded six months later, it truly takes someone with striking design and development skills to understand very complex questions sometimes. By having the bounty die-off the important question is no longer appears important and the more difficult question has a greatly reduced chance of being answered. A useful answer half a year from now is better than a slim chance of an answer that is even half on-topic.
Bounties should be fully refunded if they should expire.
Featured questions should expire without being refunded to prevent questions from perpetually reappearing in the featured questions list.
Bounties and featured questions should be allowed to coexist though after the featured question period expires the bounty should remain though the question removed from the featured questions list.
Featured questions essentially work better for more popular topics which more people are likely to answer.
Long lasting bounties essentially work better for more obscure topics which will much longer before the right person with the capability to correctly answer the question.