> My definition of a hack is to add value to the an existing system by modifying a property, not changing a zero-sum situation in your favor.
That seems like a nice definition of hack, but I don't think it's completely accurate. For example, if a college only accepts a certain number of people and you come up with clever way to get accepted, that's changing a zero-sum situation in your favor, and I would still call it a hack.
I agree, however, that the hack seems a little wrong. More clever would have been for the friends to grab another table, set it up opposite the original one with room for two lines, and then switch half the pizza boxes to the other table. (This works better than being on both sides of a single table because the way pizza boxes open typically blocks access from one side.) Another possibility would be to just grab a box each and carry it down the line offering pizza to everyone starting from the front.