Chrome is not really a Linux Distribution. Sure they're using Linux. Why not? It's a core that's well tested and does everything they need it to do. But the very reason they're picking it is because they don't care about that part of the equation.
They're using Linux to jump right to the part they're interested in which is a Web OS.
But they aren't trying to be another version of Linux or any Desktop OS for that matter. They're just using Linux as a stable infrastructure to build their OS on top of. So it's not a Linux distribution in the traditional sense. Meaning it's not really a replacement for anyone who was interested in a Linux netbook.
It's a third option not a Linux replacement