I recently joined Stack Exchange in a modest attempt to give back to the community that I've taken so much from. The experience so far has been great, although I am jealous of some of the reputation scores I see out there. Anyway...
I had my first negative experience yesterday. I downvoted a question based on my opinion that it was poorly and hastily constructed (per downvoting guidelines), and I made a constructive comment to the author requesting more information. Some other user observed this and made a rude comment about my downvote. He then proceeded to downvote all of my activity for the day.
It was a little frustrating, but I'm over it. It did get me thinking that Stack Exchange could/should have some ways to detect and weed out trolling and bullying on the exchange. I know you have moderators, and I'm curious about how they get informed/engaged when things like this occur.