They're mad at the Amazon search results because 1) Ads are now intruding in what's been an ad-free space since pretty much the dawn of the OS. 2) Assumed-private input into your OS is now being sent to a 3rd party, and you have to opt-out instead of opt-in.
Definitely a bad move by Shuttleworth; it was a fundamental paradigm shift in what people expect from an OS, crammed in half-baked, without the fanfare or discussion that was due.
That is Shuttleworth's big mistake: consistently releasing alpha-quality software in an environment where eventually upgrading is mandatory. (Because with all milestone-based distros, if you need an update to a single program, the entire system must be updated along with it.)
He's burned a lot of community karma by doing this. Witness Pulseaudio, or Unity, or now this. Day-to-day users don't want to be beta testers, they want a stable (i.e. bug-free and polished) experience, and Ubuntu doesn't deliver that.
Shuttleworth, Ubuntu, and its users would be better served by focusing on polish and regression- and bug-fixes instead of trying to turn the industry upside-down every six months. Spend time fixing bugs so I can recommend Linux to mere mortals, set up a testing lab with a wide array of real-life hardware to track and prevent regressions, and don't release something unless you'd be happy releasing it in a world where you can never update it again.
Alternatively, figure out a way to change Linux from milestone-based releases to what Windows has accomplished: A platform where the core is tested and stable, and the user can install whatever version of whatever program they like. DLL hell is a thing of the past, storage space is practically free, and Linux should be able to update, say, GIMP, without requiring an update to my graphics drivers at the same time. That way we can enjoy a stable system and opt-out of Shuttleworth's half-baked experiments.
But that's a pretty tall order.