Heh. I didn't say it was the best way, just that it was a way. And I was only referring to movie rentals. (It doesn't make sense to deliver software via USB, since it seems like CDs and DVDs will always remain cheaper than USB sticks. The dynamic USB drive isn't an advantage for software.)
Software might come on USB sticks for a while in the future, I think, but eventually even that will be delivered digitally. Valve has done this insanely well with Steam.