The only person I draft off us is DH. He is a very strong and fast rider and really, its the only way I can keep up with him. We typically pick up a lot of riders on group rides, mostly guys, and the only time it bothers me is when they try to cut my wheel to get right behind him. I don't leave any space for them to cut in, they simply drift to the right to push me over. This happens so often that I finally convinced DH that we need matching Jerseys so people realize we are together. He has no clue this is happening while he is up front and it wasn't until last years double century that we did with a friend and our friend (who rode behind me the whole time) mentioned the problem to him that he realized it was an issue. (I am drifting now, not drafting.....)

When I am alone I don't draft off of strangers and it really doesn't bother me if they catch my wheel for a while. The only time it every bothered me was when this huge guy got on my wheel and was pounding massive gears to keep up. I figured if he hit my wheel we were both going down.

Anyhow, I think Blondiebiker's original post had more to do with how close is too close. I would say stay two to three bike lengths back if you are pacing (going the same speed as the other rider), thats just my two cents though and it sounds like some might still be uncomfortable with that distance.