In they keynote Zuck said :
Today the web exists mostly as a series of unstructured links between pages. This has been a powerful model, but it’s really just the start. The open graph puts people at the center of the web. It means that the web can become a set of personally and semantically meaningful connections between people and things.
While I agree that the web is transmogrifying from a web of documents to a web of people, I have deep misgivings about what the Open Graph Protocol — along with Facebook’s new Like button — means for the open web.
So, rather than using data that’s already on the web, everyone that wants to play Facebook’s game needs to go and retrofit their pages to include these new metadata types. While they’re busy with that (it should take a few minutes at most, really), won’t they also implement support for Facebook’s Like button? Isn’t that the motivation for supporting the Open Graph Protocol in the first place?