No surprise here: Google Blogoscoped has spotted YouTube videos showing up on Google Maps when you click the “more” button (upper right) and select video.
The geotagged videos then appear and can be played within an info-window:
Google added YouTube videos to Google Earth in October, 2007. Maps and Earth are on the same platform so it was only a matter of time before the same thing was done with Maps. (Indeed, video was previously available on Maps in the mapplets/add-ons directory; now it has become much more prominent.)
We should also see more and more video showing up under individual sites/listings on Google Maps (eventually), under the “photos & video” tab: