3 double cheeseburgers - what does it mean?

Yesterday, the large fellow next to me in line at McDonalds ordered three double cheeseburgers off the dollar menu (sign of the economic times?) and a Diet Coke. I couldn't help wondering about the Diet Coke the rest of the day. Did he like the taste better? Was it a self defense mechanism - given you fill up your own drink, there's no need to call out a brand, so he was saying to himself - hey, I'm careful about what I eat?