When I went to place my first bounty about a month ago, the question wasn't mine and I almost put up 500 rep to draw as much attention as possible figuring I'd only have to surrender said rep if someone actually came through with an answer.
Lucky for me I looked into it before finalizing and found that the bounty not only wouldn't be refunded, but wouldn't even be prioritized in the 'active bounties' list over 50 point bounties since they're chronologically ordered. I went with the minimum instead and still got more views and no answers, which seems like what would have happened with 500 points anyway.
Since then I've started paying attention to the active bounties tab on the home page, particularly the 500 pointers, wondering if a similar misunderstanding was taking place more broadly and leading people to lose rep they didn't expect to lose. Currently there is one bountied question that might fit the bill for what almost happened to me; the user are put up 500 bounty on a question that isn't theirs, with only 83 rep left after the bounty.
There are also six other questions where users have posted bounty amounts that are around 50% of their total rep, and I suspect that some of this has to do with an expectation that rep will be refunded if the question isn't answered. I understand the philosophy that we gain extra exposure by bountying a question and that an answer isn't what we 'buy' with the bounty necessarily, but I think this should be made more explicit in the blurb we see when offering a bounty.
I also think there might be some merit to (partially? 50%?) refunding bounties on questions posted by different users than the bounty placer, on the grounds that this still prevents endless promotion of ones own content while encouraging us to support one another (without punishment) in asking good questions.
To respond to Martin and Gerry's comments, I am primarily taking issue with the change of phrasing implemented back in 2013:
The way it is written reads to me as "this reputation is deducted immediately and cannot be refunded if you change your mind", or in other words you can't revoke it during the 7 day period for any reason. This might just be my denseness in reading, but I think less ambiguous language would be better. For example,
this reputation is deducted immediately and will not be returned to you for any reason
or even better
this reputation is deducted immediately and cannot be refunded, even if no answer is posted
I'm not trying to die on this hill or anything, it just seems like a case of ambiguous phrasing that could use clarification.