This Google sticker (on Flickr) was spotted in London. While it’s in some ways unremarkable and like any number of similar stickers (Michelin, Mobile Travel Guides, Citysearch, Zagat, etc.), it represents something of a shift for Google and a bit of a traditional marketing push.
To my knowledge nobody has spotted something like this in the U.S. but perhaps soon.
Postscript Barry: I just confirmed that this is a UK only campaign at the moment.