I don't understand what the issue with trusting Google with one's data is. At least in my mind, it's not any worse than trusting your bank, cellular operator or government with your personal details.
Thing is, the moment Google misuses this personal information, people will lose trust in them, and they will lose business. They can't afford a serious misstep.
Using collected data from search results or emails to fine tune targeted ads or suggesting Youtube videos is not misusing information. Selling people's personal information to a third party, for instance, is what would be crossing the line. And Google have never done anything like this as far as I know.
So what's all this paranoia about?