from my exp. I spend my life parking my car in the far corner in the widest hole of every car park
It's mainly kids getting in the back doors that are the biggest culprits, they just fling the doors open.
Sadly I'm on first name terms with the guy who does my dents - generally as long as the dent is away from the very edges of the panel and door locks etc where the panel is double skinned they can get em out. From my experience chips away are a bit expensive... but that may just have been the guy that does my area, the chap I use now I bumped into in a peugeot dealer - he now does all my jobs for cash