I just noticed that calcsam, who just posted two top posts in the main section of the site, only has the 100 karma that he has, so far, gained from those posts.
I don't object to those posts being there, but how did he do that?
Edit: Question answered; Eliezer mucked around with the karma system to make this possible in this specific case.
That sounds plausible in general, but I just loaded calcsam's profile in a different tab, and it's showing that he has 160 total karma, 7 upvotes/70 karma from one top post, and 9 upvotes/90 karma from the other top post, and a handful of comments with zero karma. I don't see where you're getting the extra 20 points from.
Huh - I reloaded, and now it matches up. I was looking at the post scores on the sidebar (it was showing the post scores blanked out on the user page, which it does for posts that are too new), and the sidebar has a bit of delay between updates that could easily explain it. On the other hand, that leaves the original question unexplained. Hmm.