I see too many posts with bounties being abandoned on our site. Bounties are an efficient attention-getter device which does well to attract answers to the post. If the post is abandoned, this seems unfair to the people who invested their time in answering it.
Any user who offers a bounty is not required to award it. I often use a bounty to draw attention to a question, and purposefully do not award the bounty to anyone, for the sole purpose of allowing the community to decide which answer should get it.
I cannot agree that by simply not awarding a bounty, that I have abandoned the bounty.
As +2 rep is a paltry amount when compared with bounties that are usually in the range of 50-200. My idea is that for a bounty being awarded by its poster (not the community), to refund the bounty-poster with something like 20 percent of his bounty. This is a positive type of encouragement which hurts no one.
Except I think the behavior of only answering questions with a bounty is harmful to the community. Bounties should remain non-refundable, the entire point of a bounty, is to draw attention to the question and its answers and if none exist hopefully encourage somebody to post one.