I haven't quite figured out the subtle difference between swine and pig, though I was bemused to see The Advertiser billboard referred to the current influenza scare as "Pig Flu".
This seemed to me wrong, and then I thought that I suppose 'Swine' in this case is a euphemism, after all we don't want to panic the multi-million dollar pig industry.
It's one of those Maths things: all pigs are swine but not all swine are pigs.
In the United States, the term "pig" refers to a younger domesticated swine weighing less than 120 pounds (50 kilograms), and the term "hog" refers to older swine weighing more than 120 lbs. In Great Britain all domesticated swine are referred to as pigs
I guess this is like the difference between lamb mutton and hogget, all of which are sheep.
However if you call me a pig it seems to have a different meaning from calling me a swine. Both of which may be individually true!