As far as I understand Facebook application development - which is, admittedly, not very far - it has nothing to do with Facebook and more to do with the hosting WotC arranged for the application. They got it right when they said they rolled a 1.
I didn't care for the minigame myself but I thought it was a good angle for WotC in marketing D&D. I did see it posted on a few sites around the net so I hope it's not just existing players but potential new customers hitting the game and increasing the exposure of the brand.
With any luck having the server crumble under the load is just what the developers needed to make a case to the bean counters for a better server and continued development.