I've never had a break with a friend due to the itinerary - most of my friends ask me to plan those things because they know I travel a lot.

But I do have a couple of friends who are incredibly fickle. They plan trips, and then flake out at the last minute. So anytime I'm booking something with those folks, I make sure to book Southwest and book hotels that allow last-minute cancellation. That way, when they bail, those of us left can decide independently whether or not to go.