In a non-race situation I think you can allow yourself a little more room and still get a good part of the benefits of a draft. When I ride with family, I generally pull, my wife rides behind me, and my daughter tucks in behind her. My son generally falls off the back, because even though he's the strongest rider, besides me, he doesn't notice anythng until it whacks him upside the head, and doesn't react to it until 3 days later.

Riding with friends, we'll trade back and forth, but not in regular pace line fashion, meaning not nearly as often, and generally if someone feels stronger they will come up and take a pull rather than the lead dropping back. We still give ourselves room to make quick adjustments.

9 times out of 10, if two riders run into each other, the guy touching from behind will be the one to go down. Both may go down, but the guy in back is generally screwed.