This is a waste, and I can understand why McD's would be against this. It is because of idiots like these teenagers that ruin it for everyone else. While, it was generous of McD's to offer their French fries at a lower cost, it is a shame that these teens had to be assholes about this.
The inability to keep up with such a large order is not the fault of the restaurant, but that of these assholish teens. The reason i say this is because ANY restaurant would need time in advance to prepare for a large order of food and fast food restaurants are not NEARLY as equipped like regular restaurants, and so, they are at an even greater disadvantage when it comes to handling large orders like these and so, when you have these idiots who come in and do this, it holds everything up.
If these morons don't finish their orders then they should be brought up on harassment and public disturbance charges.