There was a user who appears to have recently benefited from serial upvoting - gaining about 200 rep within the space of three minutes. I checked the user's rep chart, and it shows that there was, at one point later on, "-50 - serial upvoting reversed."
I don't think that only 5 upvotes (for they were all on answers) were part of the serial upvoting, yet only 5 were reversed. What's up with this? If there appears to be serial upvoting on a large number of questions, why has only part of it been reversed?