n spite of an avalanche of verbal filth (and a smaller quantum of the visual variety), "Zack and Miri" is not very shocking at all. He and his characters revel in dialogue that riffs on body parts and bodily fluids, but Mr. Smith's stories are bathed – metaphorically! – in syrup and schmaltz. So "Zack and Miri Make a Porno", in spite of its sometimes tiresome, sometimes amusing lewdness, follows a gee-whiz romantic-comedy formula that would not be out of place on the Disney Channel. Two best friends who have always been in love with each other discover that ... they have always been in love with each other. Granted, this revelation occurs while they are having sex in front of a camera, but it is so sweet and predictable that these potentially tawdry circumstances hardly matter.