I think this depends a great deal on the employer and he work being done, but in general, I think it is perfectly reasonable to expect an employee to either use vacation time or make up the missed time in some way. That's what I'd expect to have to do if I missed work for any reason, weather or otherwise, unless my employer was the one telling people not to come in.
And as a manager, I'd make it clear that while I was okay with people needing to take the time in order to be safe (assuming the kind of work we did permitted it), that they wouldn't get free time off that their closer-living coworkers don't. They'd not be punished or looked down on for using time for the weather, but nor would they be rewarded with extra paid time off. Being flexible is important, but an employee shouldn't expect to be paid for time he isn't working, above and beyond negotiated benefits.
Of course, most of my professional life has been in SoCal, where weather issues are pretty much non-existant. My office has been closed twice for fires, however. The whole office was closes. Coincidentally, I was on vacation both times, and I was still required to take that as a vacation day, which irritated me slightly. The policy was that anyone who had already scheduled not to be in still had to take vacation time. It wasn't a big deal, but it's not what I'd have decided if I ruled the world.
