I was looking at the userpage for [insert-here-the-user-who-shall-not-be-named] who recently offered a bounty of 150 on a question and seemed to have a reputation of just 16. I was curious what made somebody quite so generous / desperate for a good answer to a question.
In recent reputation changes I noticed a -150 for awarding a bounty and a +99 "rep change". Looking at the reputation history since then, it appears that the award of a 150 rep bounty caused the account to go overdrawn, and it got "rebalanced" to 1.
That leads to my question: under what circumstances can one offer a bounty that exceeds ones reputation? Is there a limit?