Who Do You Trust?
All three of these services collect information from you. Browsing history. Usage history. Personal information.
They collect information to make more money; whether it be to suggest items for purchase or to present more appropriate search results leading to more PPC revenue.
But who do you personally trust?
Is it based upon how long the company has existed? Is it based upon what they offer in return for this information? Stop and think for just a moment what influences you. It's a rather interesting question.
Here's a quick article from AdWeek on most recent findings.