[dubcanada]

Facebook and Google don't care about open source... Their desire is to get people to use their search/system. That's all they care about, regardless of what pretty bow they wrap it up in.

Let's look at Google...

Android - Get people to use Google products on mobile. Adsense - Add ads to your site. Analytics - Track how users use stuff to provide better ads. Gmail - Track your email to serve you better ads. Google Search - Serve you ads.

Sure they have Dart, Angular, etc which they developed for use internally and then released to the public. But do you honestly think that has anything to do with their business model? They hired smart people, and smart people design things. Those people then released them as open source. But do you honestly believe if Google was to start (theoretically) having money issues, those products would not be the first to go?

[xorcist]

It everything to do with their business model. Joel Spolsky called it commoditizing your complement (google it).

[GeneralMayhem]

I'd expect some of the bigger R&D moonshots to go first - Loon, Wing, etc. The open source contributions are good PR with the software development community.