This site has less than 20 active users. I can imagine quite easily that a few of them vote in concert because they are more or less like-minded. I got a few rep points taken off for "serial voting". It was about 10% of my overall rep. So it wasn't indicative of any large trend that I can tell.
First, I want to make sure that it wasn't done by Yannis. As much as he tries, he does allow himself more liberties to shape the direction of content rather than control its quality. He recently challenged the motivation for my asking a certain question even though he conceded that the question's content was within the parameters of the site. Vindictiveness is not something that should be expected from the moderators. It erodes the trust in the process.