Cars, Cars, Cars... How many Miles is too Much?

How many miles on a car would you say is too much? I am thinking of buying a pre owned car, maybe an Acura or Infiniti and there are a couple that appear to be in good shape and well kept but the mileage ( in my opinion) seems high. I know the higher the mileage the lower the price tag, and the year of the car has something to do with it also. But I would like to know if about 70 - 80 K is too much?? Help me out. Thanks