Is it Rude to Eat on Mass Transit?

Chow asks whether it's considered rude to eat on public transit: "I don’t mind smelling a pungent curry in the right context, like an Indian restaurant, but not on my way home, mixing with other people’s body odor."

Granted, there are times when you gotta eat on the run. On the other hand, some people don't seem to know the meaning of "grabbing a bite to eat"—I was on the subway once and saw a guy carefully laying out three boxes of his Dominican takeout dinner on the seats next to him—napkin in lap and everything. Might've been tasty, but not a pleasant traveling experience for the rest of us there.

What's your take: do you mind seeing people chompin' down on a sandwich on the bus or a commuter train? Should a no-food rule be enforced?