Yet another random, off the wall idea.

Holographic storage. Have you heard of it? From what I understand, the problem with it is when you use the laser to mark a spot in the medium, it marks every spot that the laser goes through. Well, why not use 2 or even 3 lasers, one for the x and one for the y, and another to change the spot where the x and y laser meets. Sort of fixes that. All that is left is to solve the scarring problem. By this I mean how do you keep the medium fresh? Once an area is 'burned' how do you un-burn it?