Personifi is a Texas based startup that uses tons of statistics/maths to make the ad-market much better targeted. It’s a heavy ruby/C/R based shop. They are still pretty much in stealth mode, but they put up a blog.

They got zillions of interesting parallel computing and Bayesian maths problems. More to follow ..

One of the lessons I learnt sofar from this venture is that if you have enough data, you do not need to be too smart as things have nicely converged :-).