The thing is that Firefox is the biggest project for an independent fully open source browser not tied to a big commercial company. Google having almost a monopoly is not good for the users, because Google therefore has a lot of leverage to push certain browser technologies that mostly benefit them and not necessarily the users. It's important to have an independent browser that is not optimized for 1 particular company's technology and needs. So we can view the web from a somewhat more neutral view. And yes, I think it's Google's responsibility to adhere to the webstandards and at least test their stuff in Firefox so they adhere to this neutrality. Otherwise they are only providing their websites for the Chromium-web, and not the Open Web.
