I can see if the person has a .09, has not previously been in trouble, can walk the like, recite alphabet backwards, stand on one leg and touch their nose or whatever field sobriety test they have, etc being shown some leniency...but if they're above a .15 or so, have previous offenses, and/or can't walk the line...there's no reason not to throw them in jail.
Oh, and if you are so drunk that you decide to see if your car can swim in Lake Ruth outside of Corbin/Olsen Hall, you should not get out of your DUI, even if your friend did sleep with the arresting officer.