I'm always leary about communal pizza that has been touched. I'll eat a pie that is still intact, but one that is missing a few slices, i'm sure the other ppl had to hold onto the other pizza slice to separate it from the other, so every pizza slice left over has been touched by your co-workers.
Have you seen your co-workers keyboards? dear lord.
(yes i know obviously the pizza guys are touching the pizza all over, they're food service ppl, as you hope they're washing their hands, whereas in the office there is always that one slob who runs for the free food)