AdSense Influenced By Domain Names: Does AdSense failover to domain names when it can’t figure out the content of a page? Could be — I never get PSAs on the front page, and perhaps it’s because the “gadget” in “gadgetopia” is ensuring we get in a certain ad group.
I’m betting that distiction comes from the domain name he uses, which includes the term fsck. fsck is a commonly known command line tool amongst UNIX system administrators. Here’s my guess as to how the AdSense logic works. Google examines the content of the page, and is unable to extract a distinct topic. However, the domain name is decidedly UNIX-related. So, the default advertisment will be from this ad group.