Here’s a demo of a cool semantic app from Adaptive Blue… it’s called Glue. The app lives on top of the browser as an add-on and intelligently recognizes whatever item you’re browsing on, whether it be a book, movie, song, restaurant, recipe, or wine, and lets you see what your friends thought of it to help you make a decision.
The most interesting part of the demo is at 0:58 where he asks who is involved in vertical/niche social networks for different things such as movies (Flixster) and virtually no one raises their hand. Facebook and Myspace have pretty much grabbed the whole social networking world as far as actual webpages that people visit to interact. Now where the innovation comes in is on top of the browser and on the phone. The only real websites that have a chance these days are dynamic marketplaces (Foodzie, Etsy).