(I'm answering this from the perspective of U.S. law; your legal jurisdiction may have different laws.)
It depends on your intent. In your case, it's not likely to cause any problems unless you try to pass yourself off as being affiliated with Google—you should probably have disclaimers denying any such affiliation just in case.
If, OTOH, you were squatting on the site, intending on:
- making money by selling a domain containing another's trademark,
- or generate advertising revenue from their trademark
then you would likely have your domain seized from you (and potentially sued for damages if you reside in the U.S.).
However, since you're not squatting or trying to profit from selling the domain, but rather create a site that references a trademarked product/service, then U.S. trademark law allows you to use another company's trademark (including in a domain) since you have to in order to refer to that product/service.
This is basically the same as sites like Mustang Forums, Apple Insider, and the various gaming-console-centered communities out there with names containing "xbox", "wii", "psp", "ps3", etc. All of these sites fall under nominative use, so are perfectly legal. Google would most-likely also respect your legitimate use of their trademark.
And even if they disagreed with your using their trademark in your domain name, I haven't heard of any case of Google abusing their search monopoly to censor or punish legal sites they disagreed with. In fact, if they started skewing search results by intentionally injecting their corporate biases into rankings, then they would quickly lose marketshare to other search engines that ranked sites/pages purely based on content quality and relevance.