As of July 1 2007, Ocotillo Wells State Vehicular Recreational Areas will require whip with a flag on your ATV. (why not motorcycles?) Hrmph. Oh well, here's the specs:

The whip shall extend at least 8 feet from the ground
The whip shall have a safety flag no more than 10 inches from the top
The safety flag shall be solid orange or solid red
The safety flag shall be min 6 by 12 inches
Other flags may be below the safety flag

Personally, I'd rather everyone around me had a whip. It really does make it easier to see people. I just wish people did it on their own without having to be forced by the government.