Google has two reputations: The first is for its industry-leading, wildly useful Internet services and technology. The second is for collecting and compiling untold amounts of personal and private data to quantify and sell to advertisers.
You can't really have one without the other - many of Google's most useful services are effective precisely because they learn so much about you from your data. That's why you have to make a choice: you can accept the good with the bad, and trust Google (and its terms of service) not to do anything shady with that information. Or you can ditch Google services for the many alternatives.
Unfortunately, it's not always that easy. If you use Gmail, you know Google algorithms are scanning your personal information to tailor ads and automatically sort your emails into categories. If you've chosen to reject Gmail, Google is still "reading" many of your emails, you just don't realize it.
That's because enough people you correspond with use Gmail that any email they send you or you send them goes through Google's servers. You might be surprised how many.
Benjamin Mako Hill, who runs the blog copyrighteous, ran the figures and found out the actual numbers for his own "secure" email servers:
Despite the fact that I spend hundreds of dollars a year and hours of work to host my own email server, Google has about half of my personal email! Last year, Google delivered 57% of the emails in my inbox that I replied to. They have delivered more than a third of all the email I’ve replied to every year since 2006 and more than half since 2010. On the upside, there is some indication that the proportion is going down. So far this year, only 51% of the emails I’ve replied to arrived from Google.
What does that mean for you? Unless you can convince your friends, family, colleagues and coworkers to ditch their Gmail accounts, there's not much you can do. That's a scary thought - especially considering how close Google and the NSA have been recently.