That's one advantage i mentioned. I want to be able to get in touch with the down voters.
Most forum software trying to do what snapzu does offer three responses to reports:
Confirm : The report is good and is or will be acted upon. The user reported about will be penalized (in karma or otherwise)
Reject : The report is wrong, spurious, or otherwise should not have been made. The reporter will be penalized.
Ignore : The report is in a gray area. No one will be penalized.
Ignore is good for those cases of "We should have a rule about that but we currently don't so I can't punish that person for it.".