Jason De Filippo relates his experience with spammed Technorati:

The spammer puts in a link to something, Technorati processes the page with the link as if it were a blog. Then probably using mod rewrite to see if it’s coming from the Technorati spider or inside the Technorati ip block they get one page while the rest of the world gets another. It’s an ANCIENT trick used in the porn biz to get spiders to index certain pages but when the real person comes to the site they are presented with a bogus set of links or porn sites.

What search engines like Google, Feedster and Technorati need to realize is that by broadcasting their user agent at the door you’ve just given anyone the opportunity to bait and switch you ass all over hell and back. Unless you use generic user agents on unknown IP blocks to double check your results there is always going to be the tech to pull a fast one.

Via MediaTIC.