I sometimes hike with people who don't wait very well. Frustrating if you are one of the people in the back. Some people think a hike is a race. I like to take photos, stop and enjoy my surroundings, adjust my gear when necessary.

Three of us decided to buy Garmin Rinos, including Speedy and Speedy's GF (he won't wait for her either) - the best electronic gagdet ever! It is a combination high-end GPS/two-way radio. You can see the location of the other Rino users on your topo map! Not to mention that a radio is far superior (if heavier) than a whistle for communicating things like "I have to make a potty stop" or "you are getting too far ahead so just stop and wait for me, you toad". It also has a great rechargeable battery which lasts and lasts. I think if you are careful it will last a couple of days.

You can nag at those people who don't wait and don't look back, but it rarely changes their behavior and makes for a less pleasant experience all around. The Rino rules!