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Uh oh. What did I just give Google?

On Thursday, I downloaded Google Photos and started backing up 16 years of family snapshots on Google's servers. Struck by how much better Google Photo Backup worked than Apple's iCloud Photos Library did, I wrote a story about it.

On Friday, several readers admonished me. "Mighty selfish of you. How does your family and the rest of your friends feel about being uploaded to Google?" wrote one.

"What are those f....s doing with our photos?" wrote another. "Read the agreement!"

I had read the agreement, but mostly to make sure I wasn't giving Google permission to use the images themselves -- in an ad, article, image search result or anywhere else.

But then I read "The Hypocrisy of the Internet Journalist," Quinn Norton's alarming Medium piece about browser cookies -- she called their advent "a transcendent moment in data collection" -- and I started having second thoughts.

So I went back and re-read Google's Privacy Policy. Here's what I learned:

Google collects information about me in two ways: There's the kind of information I volunteered when I signed up for a Google account (name, e-mail address, telephone number or credit card) and the information they collect when I use their services (my IP address, my search queries, my online purchases, my telephone logs, the YouTubes I watch, the contents of my e-mail and any cookies I generate as I navigate the Web).

The latter get a paragraph of their own:

We and our partners use various technologies to collect and store information when you visit a Google service, and this may include sending one or more cookies or anonymous identifiers to your device. We also use cookies and anonymous identifiers when you interact with services we offer to our partners, such as advertising services or Google features that may appear on other sites. Our Google Analytics product helps businesses and site owners analyze the traffic to their websites and apps. When used in conjunction with our advertising services, such as those using the DoubleClick cookie, Google Analytics information is linked, by the Google Analytics customer or by Google, using Google technology, with information about visits to multiple sites.

What does Google do with that information? Here's what caught my eye: (I quote)

  • We use information collected from cookies and other technologies, like pixel tags , to improve your user experience and the overall quality of our services. One of the products we use to do this on our own services is Google Analytics.
  • Our automated systems analyze your content (including emails) to provide you personally relevant product features, such as customized search results, tailored advertising, and spam and malware detection.
  • We may combine personal information from one service with information, including personal information, from other Google services.
  • We will ask for your consent before using information for a purpose other than those that are set out in this Privacy Policy.

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That last bit -- about asking my consent -- is somewhat reassuring. Google seems to be promising that my family pictures won't show up in Google image searches without my permission. On the other hand, if one of my photos gets posted on a website, blog or social network, it's fair game. See: How to add an image to Google.

Did I make a big mistake leaving Apple's walled garden? Should I be worried? Should my family and friends? You tell me.

UPDATE: Reader 66rover99 posted a useful link to the Digital Advertising Council's consumer choice page: aboutads.info/choices/. It named the 94 companies that were customizing ads for my Chrome browser, and gave me a button to opt out of all of them with a single click.

Follow Philip Elmer-DeWitt on Twitter at @philiped. Read his Apple (aapl) coverage at fortune.com/ped or subscribe via his RSS feed.

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