I would agree that its hard to find a helmet with proper protection. I want a full cut helmet and I'm using a pro-tec right now, but it doesn't have good severe crash protection, I want one with bike helmet style foam on the inside to suck up a major blow.
Here is a picture of what I'm using.
I'm looking at kayaking helmets because they look like a good solution. I of the belief that a helmet should be required kiteboarding equipement. I did get a kick out of watching the pros in Autofocus bounce thier heads off of the rails with out helmets. I think that there ins't a good reason to not wear a helmet. I wear one to protect my head, and to keep my expensive sunglasses on my head too.
If anyone finds a good helmet for guys with big heads let me know.