I originally thought it was just a music thing too, but the core use seems to be as a meta-layer for the web. That has existed before, but people apparently use

I originally thought it was just a music thing too, but the core use seems to be as a meta-layer for the web. That has existed before, but people apparently use this one - which is the value proposition of every social-web-thing, ever. Look at the comment section of The New York Times, or any other online news source; people are tremendously passionate about the news. This brings them one step closer, interacting with the text in-place rather than at-arm's-length in the comment section. I fully expect to see multiple versions of annotations as the site grows (by region, social network, viewpoint, etc.) Is that worth [$400 million, or whatever]?