If so was it your fault i.e. you knew you were trolling and deserved it or did the administrator or moderator just decide they didn't like you?
I've been banned for all of the above reasons:
When I had just discovered how great Linux is, I signed up for a Windows help forum, trolled for a bit, before getting banned. It did piss me off at the time but now I admit, even though I didn't think it at the time, I now admit I was trolling and fully deserved the banhammer.
I got banned from another Windows forum for discussing pirate software and no I didn't post any warez links of attachments, just created a thread about it and neither condoned nor discouraged piracy. At the time I thought they were being way too paranoid but I suppose I can't expect a Windows forum which Microsoft probably regularly patrol to allow that kind of discussion for fear of being sued.
Finally, I was banned from an electronics help forum because the moderator and administrator didn't like me, despite me having one of the highest reputation scores, being a member there for four years and making 10,000 posts. All I can say is fuck him, it's his loss, I've ranted about it before but I'm not going to go down that route again.