I'm curious. Please don't list names here! I don't want this to get nasty. Just give a number.
I don't have anyone on the ignore list here and am unlikely to add anyone. I had one person on ignore on another forum but eventually removed him because even though he could be a jerk sometimes, I was still curious to hear what he had to say on certain things.
The only circumstances I could see putting someone on ignore was if they were harrassing me in a major way or if they were some sort of troll or spammer. Most of the people in the latter category end up banned anyway before I have the chance to "ignore" them.
Also do you see any type correlations to whether or not forum users put people on ignore and why they do so?