Given the sheer quantity of channels Google have available it is a little worrying. They can read your email, watch your videos, listen to your music, monitor your shopping habits, access your friends.
It's not a massive leap to assume that over the years of use they've noticed that when you listen to X artist you're more likely to purchase Y item. That they've tied certain keywords in emails to viewing habits on YouTube. That they're constructing an elaborate web of not only your viewing habits but the mood and emotional state behind them.
They can now craft the most elaborate, targeted campaign EVER.
You fire up your email and Google surreptitiously injects/rewords a couple lines to trigger a visit to youtube. Once there they promote a couple of videos for you to peruse, the soundtracks to these videos (combined with the content and previous emails) put you in the mood for a little retail therapy. What's that on the side there? An advert for an item that you really would like to have! You click. You purchase. Done.
It needn't be as complex as the above, simply weighting the "random" function of Google Play so it makes you feel depressed/upbeat/whatever wouldn't be that hard given the cross-channel data collection they're carrying out.
Hypothetical? Indeed. Impossible? No. Anything to do with the article? Also no.