True, but Google is by far the most dangerous aggregation of personal information, and the topic of this conversation. It's also a company that spends a lot of effort telling people to trust them when that is clearly unjustified.
Speak for yourself.
But doing so, it handles so much data about so much people that even with good will, it's a danger. How secret services and cops could not be interested in the huge amount of data magically made available by google services ? The aggregation itself is the danger - and the feature we all love.
I search through Bing. My email is through Hotmail/Outlook. My online cloud sync is through Skydrive. Why am I cowering from Google any more than MS or anyone else that I give huge amounts of my data too?
It doesn't take much to imagine what kind of dossier could be constructed on an individual from that data. Quite likely they do know more about many people than those people know about themselves. Of course this can be used beneficially, but it's also the exact information needed to manipulate people.
That is far more than any other service is able to aggregate, and Google's business is fundamentally about mining that data in a way that is not for other corporations.
But yes, the others are a problem too - just on an orders of magnitude lower scale than Google.