They know your phone number, your favourite haunts and just about all of your interests – even the ones you've never told another soul.
But after the latest discovery of a patent filed by social media giant Facebook, it's been suggested they may have finally gone too far.
Simply put, the creepy patent reveals that Facebook wants to analyse your emotions using the front camera of your smartphone while you're using the app, and tailor material to how you're feeling at any given moment.
The patent – titled “Techniques for emotion detection and content delivery”, and discovered by New York intelligence firm CB Insights - has been labelled an “ethical minefield” by technology experts.
A spokesperson for CB Insights said: “On the one hand, they want to identify which content is most engaging and respond to audience's reactions. On the other, emotion-detection is technically difficult, not to mention a PR and ethical minefield.”
In the patent, Facebook made up a fictitious user named Desmond Jones to illustrate how the highly controversial idea would work.
“It appears from the profile that the user, Desmond Jones, was looking away from his device during a kitten video posted by Tim Boone.
“Thus, a content delivery system may determine to exclude videos of that type in the future.
“In another example, it appears that the user has watched an advertisement for scotch. Thus, in the future, more advertisements for scotch may be displayed to the user.”
Facebook has not confirmed or denied whether they actually plan on introducing the technology. But the fact these types of plans are even in the works should be enough to send shivers down your spine.
Unless, that is, you're perfectly fine with Facebook knowing you better than you know yourself.