I recently stopped posting on a forum which I visited frequently. I was one of the high post-rate members and I liked the niche of the forum and the interaction with the other members. But the forum owner had installed a modification to the system which required re-login every time the client IP address changed. Being on an ISP which assigns dynamic IP addresses from a pool with every new computer start, I had to relogon every day.
I was surprised that such a small unthoughtful action of a forum administrator could make a long time member leave.
Can anyone share other small reasons why they left a forum or other social site? I'm not speaking of flame wars etc, just small irritating things which--after they happened often enough--made you leave?