"Also, it's not a "slight chance". All these major innovations HAVE been used for evil, from mobile phones to wide-area networking to the web. It's not just fearmongering."

This is precisely my point, these technologies have been used for evil, but would we be better off NOT having them in the first place? Everything has been used for evil, including pencils. If we loose sight of perspective and only play on the fears, then it's very much fearmongering.

I agree with you on your solution of decentralized collection being better. But I would argue that data analysis involving many data sources, including yours, is what makes a lot of the services being built USEFUL. Google Now being a good example of that. I would also argue, that targeted advertisement is much more useful to me, than non targeted advertisement.