This is very interesting. As late as 2008, Google said they don't use any machine learning in search. Everything was hand engineered with tons of heuristics. They said they didn't trust machine learning, and that it created bizarre failure cases.
I believe it considering 2006-2008 was when all the deep learning pieces came together (some parts were decades old, some 5 years, some 2 years). Google's main push in ML is with deep learning. Although, I would like to see the source too. Tried to find it using Google, but no luck! :)
