But judging from the response here, clearly lots of other people think of the box as a part of Comcast's infrastructure that happens to be portable. And from that point of view, it makes sense for Comcast to eat the cost--just like they'll eat the cost of their cable lines being torn up in the hurricane.
And I suppose that if the vast majority of people have the latter view when they're signing up for cable, then Comcast should probably change their policies to fit that model, and just charge for loss or damage caused by the user.