Everyone who thinks 15 dollars is "impossible" should realize that if the federal minimum wage kept up with the federal inflation, it should have been 23 dollars right now. Which means every business should be earning enough to pay people 23 dollars per hour, and if they do not offer that and they will "go bankrupt if they pay 23 dollars" that means they didn't increased their prices according to the inflation neither, and that is the wrong part.
We have tens of millions of jobs that corporations pay as minimum as possible, specially working people under 40 hours but do not make them work 10-20 neither, they make them work 39 hours exact so they do not have to give them benefits, and in the end we are talking about is 15 too much. 15 is not too much, 15 is exactly what every business has to pay and the ones that can't should not exist because they are failed business' if the only thing that makes them stay afloat is 7.5 dollars per hour difference, a good business would survive that and even more.
There are jobs where the staff receive tips, for example restaurant waiters. If the $15 per hour minimum wage is made applicable across these sectors, then it will impact very negatively on the business. Also, the main question is whether $15 per hour as minimum wage is fair or not. The question is whether the timing is right. The unemployment rate is at all time high, and this move will just worsen the unemployment crisis in the United States.