I checked it out with friends in low places, and it looks as though it was probably a legitimate approach, although I suspect more of the "we'd be interested in an application from you" than "sign up and the job's yours" kind. I'd have to say it's pretty flattering that someone at Google appears to think I'd be worth employing there.
Wrote back saying essentially thanks but I'm not looking to relocate. That'll doubtless be the last I hear of it.
Becuase I am a suspicious type it does occur to me that it's possibly just a random Google employee looking to earn themselves a recruitment bonus. Goddess knows how they found my CV - *I* wasn't even aware it was online. I must've put it up for private consumption once when doing one of my rewrites.