Jim, yes it can be spread in food. In fact, according to the CDC, about 50% of cases are traced to contaminated food, 25% via person to person contact (often by a vector like handrail, spoon...), and 25% unknown transmission.
The most common cause of food contamination? A food handler who has been sick within the past 2-3 days. It is VERY easy for a contaminated worker to transmit the virus to the food, and from there to the consumer. This is why food handlers are not supposed to handle food for 2-3 days after they are sick. And the sanitation scores and compliance are very important, because this virus is very resiliant and can survive freezing and similar inhospitable environments.
Am I worried about this? Not really. What most people call "the flu", or nausea/vomiting/diarrhea, is really "gastroenteritis", with viruses being a major cause. Again, the CDC estimates about 50% of these cases are caused my norovirus. Are all of these people on cruise ships? No! Most people get this virus from a restaurant, food buffet (hospital, cafe), or at home or someone else's house. Maybe because I am eating out more on the ship my odds are increased, but given that something like less than 0.01% of cruise ship passengers get norovirus, there is a good chance I won't be that 1 in 10000!
If you would like more information (yeah, right!), just do a search for norovirus on the CDC homepage. There is a lot of useful information there.