Actually, the photo with the posted link was probably not faked. Look carefully, the guy is standing in a hole, the hog is slightly in front of him; measure the guy and compare that with the hog. The National Geographic show analyzed the photo and came to the same conclusion of an 8.5' hog - the photo is real if you look closely. No need to fake it, people see what they want to see.
To me the most interesting part of the show wasn't Hogzilla at all - it was the statement that domestic pigs can go feral in a couple weeks, and their first-generation offspring will have coarse hair, long faces and big tusks.... Hogzilla has the world record for wild hog tusk length BTW.