I agree guys, but for me at least, the idea appeals as I park alongside our garage at night (the wife's car gets the garage), and I have to be really careful when opening the doors that I don't touch the brickwork of the garage.
Something like these would just mean I wouldn't have to have the carpet off-cuts I currently have attached to the wall.
With the propensity of manufacturers these days to go for clean lines on their cars (i.e. no bump strips on the doors that we had just a few years ago), it does leave the doors very vulnerable. Actually looking at the bump strips yesterday, they are made of soft spongy (but not too soft) rubber rather than hard plastic, so do think they would offer a reasonable amount of protection.
Of course if the car next to you doesn't have them or doesn't give a toss about their vehicle (or yours), then these will do nothing to guard against these sort of people.