I checked my SO account this morning to find that I had -15 rep for the day. I find this rather odd since I haven't been down voted or have any bounties out. It looks like one of my accepted answers got unaccepted but I don't seem to have any visibility into that? Is there a way to track down this phantom negative reputation?
If you like to monitor which answers got unaccepted,
save http://stackoverflow.com/reputation page everyday to your local computer,
and try diffing those when you see, you losing something.