Seen on TechCrunch:
This looks like another attempt at making the Semantic Web's goals (*) work.
It would be good if it does work, because it could improve the quality of web search results, and, as frequent users of web search know, the quality of search has been going down for some time, due to the large number of spammy sites, that use keywords in their sites' content that have no or very little relevance to their actual content, just to make money off ads.
Too early to say, of course, but it may be that this attempt may work out better than earlier semantic web efforts such as by the W3C; I've heard it said that those efforts may not have made much progress due to being too complex - something like the way the TCP/IP set of protocols won over the OSI protocols. Only time may tell ...
Update: On further checking, it looks like the Google / Yahoo / Microsoft effort is based at least partially on prior W3C work, specifically on microdata - see:
Getting started with schema.org: http://schema.org/docs/gs.html
HTML Microdata: http://dev.w3.org/html5/md-LC/
(*) Related links:
TCP/IP vs. OSI:
- Vasudev Ram - Dancing Bison Enterprises