That was the Creditnet Holiday Onslaught of Disputes. The theory was that the CRAs would be understaffed during the holidays and would miss the 30 day window or just delete. Do a search on CHOD and you'll find a monster thread on it.
How legit is CSOD? I've asked this before and didn't see any feedback regarding last year's "event"...if it did happen? When is CSOD?