Show me the source code for Facebook or Twitter or Google and you might have a real point. Show me major contributions to the code Facebook, Twitter, and Google have contributed under an open source license that are not from the respective company involved - do they exist? I sincerely don't know.
Contributing back small utilities under an open source you wrote yourself to support proprietary user privacy-violating applications you built on top of open source vs. producing open source in a collaborative embedded in a community much bigger than your own company are definitely two different models, and from what I understand Facebook, Twitter, and Google are very much in the former camp. (Red Hat's in the latter, btw.)
There's a difference between open source licensed code and an open source project. Any single person with basic coding skills can post some code up on github and give it an open source-compatible license. Does this really make that codebase an open source project? What I think makes an open source project is engaging a community full of active contributors from all different backgrounds, communities, and companies to work together to make that project better than any one company alone could make it.
Yes, Google throws a lot of money at open source via the Summer of Code program. Where's the source code for that search engine, Google? Gmail? Google Docs? What? It's not available? Oh okay. I should be grateful because you threw a whole lot of money at some students to develop more code for you to build more proprietary apps on top of. Cool.
Facebook and Twitter have provided some pretty nice code under open licenses as well. Great, thanks guys! But their core product is not open source. If it was, why do Diaspora and StatusNet exist?
Google, Facebook, and Twitter all share one thing in common - their business model relies on being a centralized network, of aggregating as many people as possible to come through their service and to keep them there. They pull some pretty nasty tricks to do that, really toeing the line of privacy and decency and respecting users. And they have to. If they start dipping in popularity they lose eyeballs on their advertising and their business falls apart.
Red Hat's business model is completely different. Their business model relies on keeping everything open so any business can deploy their own version of what they need in-house and not have to rely on a centralized provider. So they can deploy on any hardware they want. So they can build a stack with pieces from all different providers, not be locked into one monolithic stack from top to bottom from other enterprise providers like Oracle.
So again. Yes, it is fair. But I would love to learn more about how Facebook, Twitter, and Google are engaging in the open source community and innovating towards new business models that don't rely on them tracking my every move on the internet without my permission.