I really don't think anything drastic like all of us sending them comments is necessary for him to get a new pizza. Companies will often send you free stuff if you simply send them a letter saying you are satisfied, so when things go wrong they are usually very good about it. Send them the picture and I'm sure you will have multiple free pizzas coming your way.
Though if the pizza is a dollar like people are saying and 7 is the norm, well then I don't think you have much to complain about, its a freaking dollar pizza