I've been banned lots of times. I was banned from Serebii because I was sick of the elitist attitude of many of the users and protested their policies - plus I decided to troll them. I also got banned from my original Yahoo Answers account for trolling.
The biggest ban I've had was from Behind the Name. I constantly argued with the users, and made ridiculous comments that got them pissed off. I often thought the names that they liked were stupid, and when I wanted to find names for my stories, the suggestions they gave were stupid. The people there seriously think that all American parents these days give their kids names like Nevaeh, Jayden, Khloe, and Bentley, and that hoity-toity names like Hero, Tybalt, Venetia, Leander, Cressida, and Xanthe are popular in the UK (I've met many British people at camp and NONE of them had names like that). The users are overwhelmingly left-wing, and most of them are die-hard feminists. Some of them are also *** hags. They also overturned double standards - one British user thought it was okay for teenage boys to wear skirts (ick) but not okay for them to wear shorts (this is 2013, not 1900 - teenagers and adults wear shorts too). They were also very hostile to the fact that I didn't like Harry Potter and wasn't into literature. But a lot of it was my fault too - I was younger then, and I made tons of anti-Muslim, anti-European, anti-African, and anti-gay comments (I was a lot more racist back then than I am now). After my first account was banned, I created a fake account pretending to be a black girl named Aisha, and surely enough, I got banned after constantly rambling about William Zabka. I'm probably now Behind the Name's most legendary troll - I think I beat out some stupid girl from Finland who caused chaos there before I joined.