This is a good point and I agree. Given that Google has already been looked at for anti-trust violations, I'm sure a move towards disabling APK installing that essentially killed the Amazon market on non-Kindle devices would cause a massive blowup and as such they'll probably avoid doing this.

I'd still rather support a company that kept that feature in because they believed in it rather than because they are afraid of what Amazon and/or the US/EU will do if they change it. Unfortunately, I'm less sure than ever that Google will do the open thing because it is the open thing and not because changing it to the closed thing would be too painful. And that sucks.