Versions before 3.1 got hacked where only google sees a big bulk of text with plenty of text, this is so that the visitor does not get a sense of urgency into fixing the issue.
Surely, by the time the user updates the compromised WP install, Search engines would have visited his/her website a few times, and think the links are important, giving away the beloved rank to the spammer !
In any case, it seems WordPress are aware of the issue, and the update, followed by the DB update (You will see when you login as admin) resolves the issue !
Happy blogging !