I don't eat pork because Allah has forbidden it. There could be many reasons why it's haram. But from a scientific standpoint, raising pigs for food (which means raising them in large numbers as opposed to a smaller number for medical research) is dangerous. One of the biggest dangers is influenza viruses. Not only do pigs catch and transmit "swine flu" (our current H1N1 problem) but they can also catch human flu and avian flu viruses. It's an epidemiologist's nightmare that pigs will become infected simultaneously with avian and human flu viruses and they'll mutate in the pig in such a way that the deadly avian flu could pick up the transmission characteristics of the human flu viruses and become easily transmitted within human populations. If you look at the origin of most flu strains, they come out of southeast Asia where you have waterfowl (especially ducks, which appear to be natural flu virus reservoirs), humans, and pigs living in close proximity. It's an ideal environment for flu viruses to evolve. And as China becomes wealthier and its people consume more meat (pork being the favorite meat of the Han Chinese) we may see an increase in disease originating in pigs. These animals are valuable as a source of heart valves, enzymes, and medical reasearch, but raising them for food is an unnecessary risk.