Targeted un-advertising?

[vvvexation]

Weirdness. I just got an email to which Gmail didn't see fit to attach any ads at all. It was very short, just a line or two about the time and place of an upcoming rehearsal, so that might be why--but then, I got another very short email within the last couple of days that had some completely unrelated ads attached to it--ads for domain hosting and suchlike. I can see why they'd throw in random ads if there weren't enough keywords for targeted ads, and I can also see why they'd just skip the ads in a case like that, but not why they'd alternate instead of doing one or the other consistently.