I have read the FAQ and the section on bounties, where it says "If you’ve asked a good question, edited it with status and progress updates, and still are not receiving answers, you can draw attention to your question by placing a bounty on it."
And a little later, "All bounties are paid for up front and non-refundable under any circumstances."
I had a good question (5 upvotes), but no answers. I really needed some info on the problem I was having -- it was holding up a project I was working on -- so I offered a 500 rep bounty. As it turned out, I got an answer just as my grace period was starting, so I was able to award the bounty.
However, if I had not gotten any answers at all, what is the rational for not returning the bounty in that case? Particularly on a question with multiple upvotes? As it is, the 500 rep would have just disappeared into thin air.
There is a somewhat similar question that talks about the same situation, but the answers/comments don't explain why the policy is as it is (bounty is not returned if there are no answers at all on a "good" question). This actually disincentives the OP from risking his rep on a future question with no answers.
Perhaps the bounty could be returned only if the question has no answers and the question has a certain minimum number of upvotes.