I've been getting 'Failed to verify username' recently on our server.
Tried Googling it, but it came up with scattered results about Mojang's authentication servers being down. However, it's been a few days, and nothing has changed.
When set to Offline Mode, the server's coming up with errors about not logging in.
We've been running 12w07b, so is the problem with the snapshot or my network?
Would be a lot of work, but technically possible.