MySQL CEO Marten Mickos just gave at talk on at the Web 2.0 Conference on "The Great Database in the Sky".
The idea is that "structured data should be open sourced", linked, and easily accessible. The idea is to do something like Google does for unstructured data (web documents) for structured data (database records).
This is not a new idea. People usually talk about this as querying heterogeneous distributed databases. The trick is matching up disparate data definitions and smoothing over bad data. And that is quite a trick.
One technique is to require people to publish their data in some format that is easier to merge and process, but that requires all databases to cooperate. Another technique is to wrap databases with some translation layer, but that requires custom (and often fragile) wrappers for each database.
It's an interesting problem. I think there are good examples of doing some of this for specific domains -- metashopping searches like Shopzilla, Shopping.com, and Smarter.com, for example -- but Marten has said that MySQL will be leading a much broader push.