They are great for the odd occasion when you don't have racks or can't fit a board in, wouldn't want to leave them on all the time they can rub in spots and mark your car.
As for stealing them, youd have to cut them and that would ruin them so not much point in knocking off a set.
Buy good quality like FCS ones and you should have nobproblems. I have stacked 3 longboard and drove 120km/h with no probs, just check they are tight every now and then.
Yep, if you use them for a prolonged time they will soften the roof of the car. You can add an additional strap on the front to stop it lifting and putting pressure on the roof. If it's a hire car...........doesn't matter
