I don't know why some people find this ad so annoying, but I love it. Mostly because Office Space is such a good movie and because I'm really irritable on Mondays and it makes me chuckle. I think it would be even funnier, though, if the ad only appeared on Mondays. Perhaps that would silence the haters just a little bit, as well. When I see "Case of the mondays?" on, say, Wednesday, it's just not as amusing as I wish it was.
Maybe on other days of the week, the StackOverflow Careers ad could be a picture of Milton with the caption "I told Bill that if they move my desk one more time, then, then I'm, I'm quitting" or something. That's a fairly weekday-independent advertisement, I would say.