From what I know, it's actually limited in Texas (surprisingly). I think to $480 ($16/day for 30 days), but I cannot find anything from NADA actually saying that (it's just what the service manager thinks and he could easily be wrong).
Oh wow, that is quite a limit. Check with a body shop in your area. Often times insurance companies let totals sit for a long time, before they send the salvage company to pick up the vehicle.
In the case of my big storage bill, the repairs were in a dispute, a shop in Southern Illinois had tried to repair hail 3 times on a car with less then 2000 miles...they screwed it all up...I had it for two years!
I charged $50/day for indoor storage & $20 a day for outside...and that was 2002.

I would also add on estimate, teardown and admin fees.
Like you mentioned, the storage fees encourage the vehicle to be picked up. I knew of shops that did not charge storage and they would end up with totaled out cars sitting on their property for months....