They used two different mood-calculating tools, but only one worked, and only certain moods were predictive! By default, they noted that most users were English-speaking and US-based! IDK re: sample size!

I think they then incorporated it into other stock-market predicting tools and it improved the models predictions, but I had stopped reading closely at that point :D

http://www.mediafire.com/?fiozw0w9ogcmm74 if you are interested