ChromeOS does not give the possibility to install any binary software,
but as it comes with some binary plugins (flash, pdf?, native client?)
preinstalled under the hood, I had thought it's not too much beside
the point that it would provide a more complete experience of Google
services and Google's earth vision.
Trying to make Google Earth work on all distributions is in my eyes a
very huge and ambitious project (they could also just make it work
with standards and debian, forcing the excrescence of smaller
distributions to go compliant with bigger distributions). The move of
the Google Earth client to LSB might be a step in that direction. Now
as there exists a native client for some years, the problem of
creating a native plugin isn't the same as creating a completely new
linux port of an application.
Unfortunately Google Earth is not open source (in contrast to chromium
etc.) so there is much will but not much chance to help Google. One
opportunity for Google to get some help could be the GOOGLE SUMMER OF
CODE.
I think the most current numbers on
canonical.com is something around
15 millions (growing 2-3 mio. per year, but that doesn't say much
about Ubuntu-only users or now-and-then users).
I once made a Google Earth Plugin web app, (programming blindly in the
dark, and sometimes testing on windows). But as I almost never used
it, I had not much motivation to do more (although I like Google
Earth).