Future Precedent?

Is the NFL is setting itself up for future trouble with its pious explanation that the postponement was out of concern for the traveling safety of the fans. Cris Collinsworth seems to think so.

How much (or how little) snow does there have to be for the NFL to concern itself with fan traffic in future games?

4 inches?

6 inches?

 8 inches?

10 inches?

 a foot?