I feel it really depends on the topic and the community. Do you have examples where you saw it and couldn't explain it to yourself by looking at the content which has been downloaded?
I can help with this one. We just really don't like people coming over here trying to find out how to get BACK onto another site that doesn't want them.
There's a surprising amount of those, but that's very specific. Maybe other people from that instance just make stupid posts?