What baffles me about this whole thing is that the supposedly user-hostile behaviour is easily turned off, isn't it?
The defense team sometimes overreach, too: "not an ad?". It would be more honest to me if Shuttleworth just said:
"Hi. Amazon was so kind as to strike a contract with us, and we will search amazon online when you do a dash search. Yes, there would be ads for products selling from Amazon, but they are nice guys, and the money will help us make Ubutu a better OS. If you are concerned with privacy issues, turn it off by doing so and so. We rather prefer that you didn't, because, you know, we have to eat too, but ok!"