Does the Google/Bing/Yahoo Schema.org Markup Promote Invalid HTML?

[Update on 10-Jun-2011: The answer to the question of the title is “not really” — see the update at the bottom of this post and the comments for more information.]

Yesterday Google, Microsoft Bing, and Yahoo! announced a project to promote machine-readable markup for structured data on web pages.

Many sites are generated from structured data, which is often stored in databases. When this data is formatted into HTML, it becomes very difficult to recover the original structured data. Many applications, especially search engines, can benefit greatly from direct access to this structured data. On-page markup enables search engines to understand the information on web pages and provide richer search results in order to make it easier for users to find relevant information on the web. Markup can also enable new tools and applications that make use of the structure.

The problem is, I think, that the markup they describe on there site generates invalid HTML. Did they really do this?