The big promise of linux was that it would commoditize the OS market, and this is exactly what happened. It is indeed a victory for linux that everybody who wants to build their own OS starts with the linux kernel. The OS can move out of the way, because it should have never been in the spotlight in the first place (this was a larval phase of the personal computing market.)
The upside should be that everybody contributes back into the global pool of source code, and that even people who would never buy a chromebook benefit by google's source contributions. I don't know how that works out in practice though.
Not to mention ChromeOS is open source (http://www.chromium.org/chromium-os), happily accepts patches, and the chromebook has a built-in developer switch on it that you can flip and install what you want on it.
Pedantry: BBX hasn't shipped yet outside the PlayBook, and I'd hardly call that popular. The phones are still running the original since-1999 BlackBerry OS.
And why not BSD? I'd mainly say mindshare, and portability to a degree. You don't have to release your source every time you port BSD to a shiny new platform. BSD code is out there (networking stacks, a handful of the base *nix utils in OSX), but the permissive license cuts both ways.
BSD is used in a lot of places, it is generally hidden though. For example Juniper used it for their OS, FreeBSD is currently in use by NetFlix for their appliances (the ones that sit on the ISP's network to lower costs). Cisco has in the past used code from BSD, I've seen OpenBSD in various different commercial projects, including an audit logging machine.
Every so often I get surprised as to where BSD is when I come across it.
I'd say that the choice of Linux over BSD on those cases has to do with hardware support. Writing drivers and supporting a wide range of devices would increase up a lot the development time for Chrome OS, for instance.
Industry settled on Linux in the 90s when a) there was lingering FUD from the AT&T lawsuit, b) everyone was afraid of "embrace and extend" which the BSD license arguably makes easier.
The upside should be that everybody contributes back into the global pool of source code, and that even people who would never buy a chromebook benefit by google's source contributions. I don't know how that works out in practice though.