We're just hearing about the Technorati Keyword Search feature. We'd love to query the Keyword Search API to post links to related sites along with new entries to our site, a feature that would be technically trivial to implement, but something we'll probably never do because the API merely returns links to each site's front page, not permanent links to pages containing the searched terms.
John Dowdell points out another problem in a comment posted to Technorati creator David Sifry's site:
Hi David, I'm glad you did this, thanks for the work, but... is there any way to index on the individual RSS entry rather than on the whole HTML page? I'm getting a lot of false-positives on two-word queries, where the words actually occur in separate items.