You would think that an outfit as large as Google would do a trademark search before rolling out a service:

A trademark dispute has forced Google to re-brand its Gmail web mail service in the UK. Existing users get to retain their Gmail address (at least for now) but from Wednesday onwards new UK users will be given a Googlemail email address instead.

UK-based financial services firm Independent International Investment Research (IIIR) said its subsidiary ProNet Analytics has been using the Gmail name for a web-mail application since the middle of 2002, two years before Google began offering Gmail accounts to consumers. The email service offered by ProNet, by contrast, is used mainly by investors in currency derivatives.

I suspect that the problem here is a US-Centric one - I bet they looked in the US, saw no problems, and went ahead with a world-wide rollout. This is going to be a big problem for companies over the next little while.