So, where can I download my own, Open Source, copy of Google's search algorithms and databases? Or of their other moneymakers? G-Mail? Google Apps? Google only opensources stuff they don't really need.
Google uses open source software the way is should be used by companies.
The point of open source is not charity. For FOSS to work, it needs commercial players, and you won't make money just by giving away stuff. Open sourcing must be profitable somehow.
So obviously, you won't open source your moneymakers in a way that can help your competitors. Opensourcing Chrome, Android or a few libraries, however, makes a lot of sense. These products only serve to support their moneymakers, Google doesn't intend to profit on them directly. As a result, they lose very little by opensourcing and they gain reputation and potential help from other developers. It's a win-win situation.