Photosynth demo is certainly impressive but I am more excited about where it leads to. If one can weave all the photos online into a single world fabric, imagine what will happen when you add video. One minute video taken by a tourist anywhere contains, on the average, 900 frames. Even after accounting for lower resolution, redundancies, and motion artifacts, there are a lot of information there, particularly 3D hints.
Now imagine a virtual world that is built entirely out of all the photos and videos uploaded to the Net, one that is constantly updated and missing parts filled-in over time as camera-wielding tourists roam the globe, a world that offers new business opportunities. A service like Like.com can let loose spiders into that world to tag products with price and shopping information. Enterprising individuals can also offer richer experiences for a fee.
Fun stuff.