I get uncomfortable when a rider I do not know jumps on my wheel in order to draft me. There are risks involved in tight drafting where the front wheel of the drafter can overlap and touch the leaders wheel causing a crash.

I'm posting this to see what others have said/done to be polite about expressing to another cyclist that you would rather they not ride your wheel.

Obviously I will drop the ones I can but sometimes I get a sucker who is just strong enough not to drop.