The long-term downward trend is typical for almost any new product when you look at only the US market. It corresponds to market saturation, and "everyone in the US" becoming aware of the particular search term.
I personally prefer the simplicity of a paper book. I only use Kindles for stuff like travel guides, where I don't want to lug a heavy Lonely Planet paper book around, or if I need something immediately.
Is it more acceptable in certain regions? I guess Milan is a pretty important city, so I can't see the Mafia being tolerated. But what about for small shops in villages etc.?