Seems like the market is moving to almost all second-tier browsers (e.g. Opera) building from Chromium. I think this is a positive development as it should strengthen the underlying code if more people use it as a standard and then innovate UI, tools, services and so forth on top of it. Similar to what you see with the custom Android flavors/knock offs/whatever you want to call them in China.
I can think of many reasons why folks would want to use a custom browser built on top of Chromium rather than Chrome. Take Opera for example - Adblock and VPN are two services that can live more efficiently deeper in the core versus the extension layer where they are on Chrome. And these are two services that Google does not want to promote any more than they have to in order not to shed users. Browser competition is great for the market, the last thing we want is to end up in an IE6 type situation (and yes it can happen to anybody, even Google).
