As that crash video shows, even a small heli can destroy a large model airplane. And typically it's not going to be the speed of the rotors but rather the combined speed of the two converging objects. My objection is that the flight path of helis (and we're talking here about those awful 4-D aerobatics) is frequently unpredictable. I don't mind flying with 2, 3, even 4 other aircraft in the sky because I know more or less what they'll be doing.

Anyway, so far it doesn't seem like it's going to be a problem for me at my new club. I've been to field three times, seen a total of three people, and two helis. The heli guy flew once and went home.