I don't really know how it got set, perhaps I did it while clicking around, but I don't recall doing it. One of my sites had the privacy setting set to block search engines. Big oops. I was wondering why updates didn't seem to get indexed anymore.
It's worth a moment to check yours.
Settings | Privacy
() I would like my blog to be visible to everyone, including search engines (like Google, Bing, Technorati) and archivers
() I would like to block search engines, but allow normal visitors