Q:

Serial downvoting on MSO

I appreciate that the logic used to identify serial downvotes is kept private and generally I could care less about my rep (considering it is funny-money afterall and I care even less on meta sites where it is even funnier-money) but I am curious.  I've recently been a "victim" of what appears to be serial downvoting based on my response to this meta question (yes I realize that 2 downvotes generally probably aren't enough to trip the sensor) but it seems awfully coincidental that I leave a couple comments that could be seen as negative on a question and suddenly I receive 2 downvotes within seconds of each other. 
Without exposing too much about the serial downvote sensor's inner-workings, would someone be able to help me justify this for my own peace of mind? 
I understand that it is possible that 2 different people could downvote me at the same time (though not likely considering my limited number of questions and that they downvoted 2 questions that were generally upvoted). 
Is it common practice to see serial downvoting on MSO as one would expect to see on SO?   

A:

It's basically the same thing that we see on Stack Overflow.  Someone stumbles into an answer you wrote and doesn't like it for whatever reason.  Then, they look at your history and find a few other posts that they don't care for. 
This behavior often isn't intended to be hostile, at least in my experience.  Users just realize the importance of voting and feel as if they're doing some sort of civic duty.  We typically just have to remind them that voting their way through another user's history is bad because they're focusing on an individual, not just content and quality. 
In short, there are a few common mistakes that users make while the proverbial training wheels are still on the bike.  This is one of them.  Yes, I have caught a few people red handed when the intent was clearly revenge, but those have been very isolated cases. 
When analyzing the behavior of others (especially on The Internet), Hanlon's Razor should be liberally applied:

Never attribute to malice that which is adequately explained by stupidity. 

In this case it's often not stupidity, just a bit of a learning curve when it comes to getting to know the rather unique system that is Stack Exchange. 