I am slightly paranoid about door dings. I found the best protection was to park in protected spots or away from other cars.
I work in an office building with 5 floors of parking, but only use the same 5-6 spots, all protected on both sides by pillars and away from heavy foot traffic.
When I have to park elsewhere, I try to park where there are fewer/no cars and away from heavy pedestrian traffic.
It of course means I have to walk more (not a bad thing

) and it drives my wife nuts (she likes to park IN FRONT OF THE MAIN ENTRANCE!!!

), but my now 4 year old car has NO dings..