Have you noticed that whenever you open an email in Gmail web interface the ads served to you are connected to the email content? If you don’t believe this, look at the pictures below to see the connection between an email received from a bank and the add for another bank and an email received from trip advisor and ads related to travels.
Google is having an explanation: “This ad is based on emails from your mailbox. Visit Google’s Ads Preferences Manager to learn more, block specific advertisers, or opt out of personalized ads.” And if you dig more you can see that your emails are scanned in order to get the most relevant ads:
How ads are personalized on Gmail
In Gmail, most of the ads we show appear next to an open email message and are related to the contents of the current email conversation or thread. These ads appear on Gmail regardless of your preferences or settings. In your inbox, you might also see ads that match the contents of one of the emails in your inbox.
When we personalize ads, we display ads based on the contents of all your emails. For example, if you’ve recently received lots of messages about photography or cameras, we might show you a deal from a local camera store. In your inbox, we might also show you ads related to information from different emails in your inbox
Even if this is not done by humans and even if Google assures the users that their privacy is respected, the concern is still there. And Microsoft is taking advantage of this, trying to promote their Hotmail and Office 365 services in a blog article posted recently on their official blog (full article can be found here) and criticizing Google for scanning your emails:
Some email services, like Gmail, actually read the contents of your mail (both sent and received, even if you aren’t a Gmail user but just sending to someone who is) in order to decide what kind of ads to serve up to you. They may call it “scanning” and attempt to equate it with less invasive activities like “checking for spam” but it’s quite different. For you, and the people you send mail to, it’s not spam, it’s personal.
Does this sounds scary? Here is some more stuff to think about: answering the question on Quora: “How many Google employees can access Gmail data?” Christopher Cuong Nguyen, former responsible for Google Apps operations at Google Gmail says:
A small number of Gmail-related engineers have access to the servers as a matter of necessity to do their jobs; a very small number of people actually access the contents as a matter of necessity to do their jobs, and even then, almost always only the associated metadata. The rest have to file a request and justify any access they ever need, which is extremely rare. All have to sign paperwork re users’ privacy at the risk of dismissal & legal action, knowing that whatever they do is discoverable. And ultimately, an internal culture of respecting users’ privacy helps keep one another in check.
So the risk is never zero, but minimized by the factors above.