This is really great : try it !! For example, I made a Search limited to your delicious bookmarked sites.
OK It is a BETA : a bit unstable or maybe it is my browser and a bit slow and not perfect yet, errors doesn’t seems to be reported, but once it will be reliable, this will be great.
(Looks like it is very server side for now. So maybe they have to much success.)
At least, that kind of tool may drive the adoption of more “processing friendly” techno, like XHTML and other Semantic-web stuff that only geek seems to care about now.
Via Yahoo! Pipes: Unlocking the Data Web. Read it, it gives much more info.