I nearly got as far as setting up an Open Data Table definition for WeFollow, so that it could be queried using YQL. Sadly the HTML parser that YQL exposes for arbitrary URLs isn't available to web services defined using Open Data Tables - they have to return either well-formed XML or JSON.
Still, I like the style of the Open Data Table definitions, and found some useful documentation in Chapter 5 of the Yahoo Query Language guide ("Using YQL Open Data Tables").
There are lots of community-contributed definitions in Sam Pullara (of Yahoo!)'s GitHub.
Also, it would be great if YQL could use CSS selectors, in the way that Freebase's Acre does using Sizzle and Rhino, alongside the existing XPath selectors that are available for use on parsed HTML.