First, I use a Crain Tri-Max. Second, I'm hyper sensitive to what you are talking about and that SOB is stable and better be tough to get out at the end of the set up. Third, I check those legs regularly to be tight when I'm working with them, like once or twice a day. If the quick release seems a little too easy, then the leatherman comes out and it gets a tighten.
I haven't had a problem with it ever though.
For really strange set ups, like on concrete, I have been known to (A) set up the tripod with as many feet in the dirt as possible and (B) for those legs on the concrete, if I can't get it in an expansion joint, to chisel a hole (like you would use a star drill), with a 60d nail and get it so such a depth that it would really be difficult for it to come out. Takes about 5 minutes per hole but the metal spike fits snugly in the hole. Almost 100% of the time, I pick my setups such that I don't have that issue.
We recently did a topo where I had to have, at three points, at least one leg on a concrete sidewalk. Each one of the nails was set in the dirt and in a projection of the wooden expansion joint so that two legs were firmly in the clay and the other in a piece of wood. Makes a big difference.
The people who don't pay for it don't think like this though, unless you train them to think like this.
