“Let’s run through a little thought experiment.
Imagine there’s a list somewhere that contains every single webpage you have visited in the last five years. It also has everything you have ever searched for, every address you looked up on Google Maps, every email you sent, every chat message, every YouTube video you watched. Each entry is time-stamped, so it’s clear exactly, down to the minute, when all of this was done.
Now imagine that list is all searchable. And imagine it’s on a clean, easy-to-use website. With all that imagined, can you think of a way a hacker, with access to this, could use it against you?
And once you’ve imagined all that, go over to google.com/dashboard, and see it all become reality.”
What Google Knows About You | WSJ [more]