I've been giving out a few bounties recently on some tough to answer questions, but they've mostly been dismal failures without even generating an answer.
The data on all bounties seems to back this up, with roughly 25%1 of all bounties on questions expiring without even having an answer with 2 upvotes needed for an automatic reward of half the bounty. Some didn't even generate a single answer.
1The Holiday Bounty Giveaway probably skewed the numbers in favor of successful bounties by a bit, so real bounty success is probably worse than the data.