SWATTING. Not only did it happen to Krebs ( http://www.cnet.com/news/security-reporter-hit-by-swatting-attack/ and http://krebsonsecurity.com/tag/swatting/ ) but this is now a tactic used on folk by other avenues. It's quite possible for someone that has a grudge or just for fun take you offline.

Just like the police, ATT and other companies are not ready for this.

Mind you I didn't say it was right or such but it could have been other than what you led with.

I would be guessing what your business model is here but it looks like someone took you out. It could be a misbehaving client (user?) It's a shame folk could inadvertantly do that with a malware infection.
Bob