One of Red Hat's superpowers is in hiring relatively unknown developers, and helping them become strong participants in the open source world. But their compensation isn't super high, and when you travel on Red Hat's nickle you have to share a room with someone else --- assuming you get travel approval to go at all. For people on help organize conferences, Red Hat is rather infamous about having their full-time employees ask for travel scholarships, which originally established to support hobbyist developers.
As a result, it is not at all surprising that Red Hat ends up functioning as somewhat like a baseball farm team for companies like Facebook, Google, etc. who are willing to pay more and have more liberal travel policies than Red Hat. If someone can become a strong open source contributor while working at Red Hat, they can probably get a pay raise going somewhere else.
There is a trade off --- companies that pay you much more also tend to expect that you will add a corresponding amount of value to the company's bottom line. So you might have slightly more control over what you choose to work on at Red Hat.
Nope I love Red Hat and loved working for Red Hat and still interact with most of my colleagues there on a day to day basis. I shouldn't be speaking for everybody, but from what I can tell we're all pretty happy where we are, so no real reason to switch companies.
I think there are some ways that RH would be less desirable for many people than a BigCo. When I was interested in working for them they had offices in inconvenient locations and a requirement that you (or at least, I) work in one of them -- e.g. their "Boston" office is 30 miles away in Westford, and their headquarters are in North Carolina. That's disqualifying for many people.
I imagine they pay significantly less than the other companies (e.g. Facebook) who want to hire Btrfs devs can afford to, too.
