I will agree that there is some commercial benefit to Google for this sort of thing, but even I'm not cynical enough to think that's their rationale for doing this.
Freddie Mercury was one of my biggest heroes growing up, and I thought this was really nice (and maybe will cause a whole bunch of young people to ask "Who the hell is Freddie Mercury?").
There's no question Queen was a fully-sold-out pop band at the end. With their talent they could have easily pursued a less commercial path--and in their early albums, had a fair deal of influence from heavy metal and progressive rock--but for whatever reasons, they didn't. Not a criticism, just a fact.
It is a tribute, with at least some degree of creativity and effort put into making the video. I don't see this being exploited to gain Google any more users than, let's be honest, they would have anyway. Especially since it is on Google Japan, I would anticipate people going to the main page, watching the video, and then not even performing a search. And in instances where that does occur, Google is gaining nothing financially from something which, again, is a creative tribute.
I don't really see it as shilling at all.
Somebody took a copy of Super Mario World for the Super Nintendo and hex-edited the levels so that instead of requiring a human player, the game's built-in physics propels Mario through the level. And, the levels were designed so that the various sound effects caused by Mario stomping on and bumping into things vaguely approximate the music to Don't Stop Me Now. AND four entirely different levels were created, each attempting to reproduce the part of some particular member of Queen. AND they occasionally sync up for the more spectactular parts of the song.
One of the most impressive examples is an 11-minute medley of video game and cartoon themes: http://www.youtube.com/watch?v=Xz0PaPpmGa8
There are some good examples already (the GTA4 negative wheel friction hack (http://www.youtube.com/watch?v=I0cUkU9rZyE) or some of the Mario64 Tool-Asisted-Speedruns come to mind), but we're not yet anywhere near these beautifully orchestrated sublimations of classic Mario, Zelda and Super Metriod.
Not really a mod - but certainly has the love/devotion thing down.
It's also absolutely amazing, I recommend you to watch it in it's entirety.
(I think it's also no longer Japan only, it was on .pl and .com for me also, but YMMV.)
Edit: blog says that it's appearing in the US on the 6th. http://googleblog.blogspot.com/2011/09/happy-birthday-freddi...
That's probably the most time I have ever spent on the Google front page, maybe that's a hint to advertisers.
At the end it auto-googles him too, isn't that a first too - Google auto-forwarding?
