Seven at the moment.
At any given time, 3 or 4 are usually banned so there is no real benefit to me. I find the vast overwhelming majority of people's posts here interesting from one perspective or another but there are a very small minority that are either so immature, make nothing but flame or troll posts, or are just pure imbeciles that I've found that my life here is just that more pleasant with them on ignore.
I ignore folks like this in real life too, so I'm consistent in this regard.
I'm one of those people that post in P&N and the majority of them on my list are active in that Forum. I've got one individual on ignore that posted so much garbage in The Garage forum that they were banned from there permanently. So, I personally don't feel that my reactions to at least some of these folks is over the top.
I actually feel sorry for the mods because they can't ignore anyone. I'm pretty certain there's at least one or two that wish they could ignore me.