There is a great little saying, "Better safe than sorry." If you're going to be DD, just suck it up and don't drink. If you want to drink, just wait til next time; the DD should rotate unless you have someone like Gadough who doesn't want to drink (and Gadough, when you DD make sure you drive someone else's car incase someone ends up puking). A lot of bars will give perks to the DD too. At one bar where I was an undergrad, DD's got free soda all night, and could order one appatizer free of charge.