Mike Rose and I were chatting about this on the Talkcast a few weeks back -- virtualization and emulation programmers get all John Locke from Lost when you try to tell them what's not possible. And so when the guys at CrossOver heard that Google wasn't releasing Chrome for the Mac, they decided to put together a release themselves. CrossOver Chromium is a proof-of-concept release of the Chromium browser (which Chrome is built off of) that allows Google's base code to run on Mac and Linux platforms.
It's designed to show off just how well Wine works to bring Windows-based code to other platforms, and wake Google up to the fact that if they wanted to port Chrome over, they could. CrossOver says they did this to prove a point (and the point seems proven), but it's likely not only that Google wants to run the code natively, but that they wanted to focus on their largest audience first, which anyone can tell you is likely still the Windows crowd.
Even CrossOver says their version isn't ready for prime-time yet, they just wanted to show how fast it could be done. Let this be a lesson, Google: don't tell virtual software developers what they can't do.