Stuff like this strikes me as a bit sclerotic and shortsighted. Sort of the techno-utopian flip side of the Malthusians of the 70s[1] arguing that food will run out on Earth.
The direction of the cost of storage (down) is predictable. But human behavior is not. And the impact of future innovation on human behavior is also not predictable. That's why oil could drop 50% in the last 60 days. It's why Paul Ehrlich and John Malthus were wrong. And why Dropbox could end up being a truly great company.
When we're filming 1 TB/s holograms of our kids playing baseball, Dropbox's free 500 PB tier just isn't going to cut it!