what if it malfunctions? Car can't start, late to work, then have to pay someone to come fix it/buy a new one/tow it to the repair man. As others have said have someone else blow into it. Also, what if you use mouth wash with alcohol in it? What if someone tech savy finds away to easily disable it or bypass it? There are lots of problems that create a hassle for the average person. And as recon said you are judging everybody because some knuckle head drove home drunk.