Agree with dkarwh, people that ride based on hand signals are very foolish due to the always grossly ambiguous information. It is usually very hard to see the fingers, you never know if there are groups traveling close to each other, and I believe we should always ride "watching out for the other guy/expecting the unexpected". Speeds being what they are in QC also leave very little margin for error if one takes their hands "off the wheel". Pure foolishness as far as my $.02 goes -
Our group has always used Collett Communicators and these to handle allot of the situations Greg covered regarding intersections, breakdowns, road crossings, etc. Additionally, they can warn of an oncoming group or grooming equipment - but we never depend on this either.
30+ years of riding likes to stick with the "Expect the unexpected" and "Always watch out for the other guy" mantras! Safety is no accident!!