And most folks aren't going to go to a black market to get trans fats - a black market for cigarettes already exists and banning it entirely would only prop it up.
True, but people might get pissed off if they notice there food tastes different.
Kraft Dinner pulled off a real marketing coup here: they removed artificial flavors and colors, and some other less popular ingredients, from the recipe for Neon Orange Macaroni Powder, and quietly pushed it out to markets for a few months.
Followed by an advertising blitz along the lines of "Will your kids like the new Mac & Cheese? They've already had it!".
To a point - it isn't like this doesn't happen without regulation though. Folks get over it.