Sorry about that everyone.

I've investigated the problem and I'm pretty sure it wasn't a problem with the source code or Bitcoin handling code. It seems to be something stupid I did with the database that let someone change their balance. This won't be a problem with the real version as the Bitcoin daemon as built-in checks against this kind of thing.

I've fixed the problem with blank usernames.

The site should also be back up.

I apologize for the fuck-ups; by software standards, we're still in the alpha stage of testing (hence why I released a demo first) and I'm happy we're catching the bugs now rather than later.