There was a defined number of Startup School attendees, which means the amount of pizza needed is easily calculable (X participants * Y slices each.. maybe + Z

There was a defined number of Startup School attendees, which means the amount of pizza needed is easily calculable (X participants * Y slices each.. maybe + Z "extra, just in case"). From hosting numerous events, I would definitely expect YC to have "how many pizzas do we need for X people" reasonably well figured out. I would think the greater danger is from people eating Y++++ slices each rather than a group of 3-4 sharing a box and having 1-2 slices each. As limedaring mentions below, we also handed out a few slices to others. To your point of the "better hack", we advocated the "use both sides of the table" for breakfast, but with pizza it is unwieldly because the lids of pizza boxes only open one way. Yes, reconfiguring the tables would have also probably improved things.. but is much more difficult with 25-50 people trying to access the pizza boxes, and no readily available unused tables on hand.