Originally Posted by SteveE
Let me also say that I think the odds of a unskilled cyclist staying that close to your rear wheel are highly unlikely. Most cyclists without good bike handling skills would be terrified to ride that closely on another rider's wheel.
But good bike skills are no guarantee of good personal skills. In my community you do get strangers that will hang on your wheel and are good riders. So, it really comes down to asking permission of the rider to be sure you both are comfortable with the situation.