I've had a few close calls over the years while grooming. The worst was meeting a young guy coming around a blind corner. He was going way too fast to stop so he threw the sled sideways. We both got stopped, but he fell off and rolled under the front blade. By the time I got out to make sure he was okay he was back on his sled and gone (probably expected me to rip him a new one).
I prefer to groom late at night to avoid traffic (it's also easier to see them coming). As another poster said, the longer fresh trail sets and freezes, the longer it lasts. If you meet a groomer, pull over as far as possible (on the trail) and let them pass. Note: After passing DO NOT drive onto the fresh trail in a full on powerslide (groomer operators hate that!). If you come up behind a groomer (yeah, we can see you), relax until there is a safe place to pass. A drag full of snow can be tough to get started again. If we can spend all night in the woods making trails smooth, you can wait for a a few minutes to safely pass.
Groomer (8000-9000 lbs) vs Sled (500-700 lbs) = Groomer wins!