That's what I was wondering too.
G = 00
A = 01
T = 10
C = 11
i thought the same thing.
maybe they did it simple for some sort of redundancy or something...
im not surprised by this though. i have always thought data will one day be unlimited in storage and speed. its just one of those things where you know its physically possible we just havent found a better way yet. i like this biotech though, the more we try to advance technology the more we end up mimicking nature.