It's important to see that there isn't just one legal perspective. The law tends to be incredibly malleable, so in many areas (especially newly developing areas of law) you'll see actors espousing theories based on what they want you to see. Think of it like a Rubin vase (http://en.wikipedia.org/wiki/Rubin_vase).

Here, it's not surprising that the government wants to take a position that gives them greater power to snoop around in files you store in the cloud.

It's perfectly reasonable to look at your data in the cloud like a safety deposit box. But alas, government tends to follow a path that gives them greater control and not less. This is just another instance of that tendency.