Printed or Digital Form: How Much of a Distinction is that Today?

This online bibliography evolved from a treatment of printed documents exclusively, but how much of distinction is there always between printed and digital documents today? Considering that many historical monographs are now offered for sale by their publishers both in print and digital form, it would appear that the distinction between print and digital in scholarship is blurring. That being the case I will, for the time being at least, continue to cite the printed form of publications unless they exist only in digital form.