Vending machines should have some sort of confirmation step.  All I have is bills, so i have to stick in $2 for the brown sugar pop tarts that cost $1.10 there in E2.  But as I press the buttons and hear the mechanical contraption spin and whirl, It's the $1.85 ho-hos that are being spun to me.  BAH.  That was F2 for the pop tarts.  crap.  Vending machines are the devil anyway.