As I spent 2 years in the image processing field of CS I thought I'd publish a link to this exciting presentation. It is more than a year old actually, but kept my attention drawn for the whole presentation.
Update: I have just installed the required browser plugin and software onto my PC and checked out. Of course: the more pictures you have semantically tagged together the smother your 3D browsing expirience will be. Thus by quality of your experience you may identify either 1) how popular the place is for photo takers or 2) is that service developed and attracted lots of people posting their tagged shots. As the 2) refers more to online service, the offline software gives you a way to build your own semantically clustered picture space.