These fences are more than "light fence" and "chain link fence". A plain old chain link fence would not withstand a car hitting it at 20 MPH without falling completely over. And I think what made the accident worse was that there was a cross-over gate where the car hit the fence, so that helped rip the car apart even more.

I've been to Michigan International Speedway ~12 times sitting in the front row for handicapped seating (for a family member), and Daytona & Charlotte once a piece, and I've thought about situations like this before, or the Carl Edwards crash at 'Dega a few years ago, when sitting there. When cars going by at 180+ MPG only 10-15 feet away, there is little you can do.