All great info. Again, I must stress that my query was not motivated by any ill will about being dropped - I just wanted to be sure that _I_ was not causing any problems in doing so. I'll be more vocal as I fade away next time... a simple, "Don't wait for me" should suffice, yes?
It might be good for the forum admins to create a "sticky" thread that could stay at the top of this forum, the content of which would be an evolving "rules of the road" for group rides. The comments in this thread will slowly march off the bottom of the forum and will be missed by others who would benefit from reading them.