Just got in from my Thursday nite ride where our small but dedicated group practiced paceline. When it works - absolutely amazing! We were going thru town and it felt like we were coasting at 23 mph. But as I was riding I thought of the previous posts and was very thankful I was with a group of riders that I have ridden with and know their skill levels. There were a couple of sharp turns where it could have been a disaster.

Great skill to learn, but frequent practice is needed especially for us newbies.
I now know not to assume it is ok to draft from someone who does not know you, but I also agree there are polite ways of letting someone know it is not something you want them to do. The idea of slowing down to discourage someone who doesn't respond is a hoot!

Thanks for all your feedback!