How do Facebook ads know EVERYTHING?

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Facebook basically spys on you. If you send messages or email or IM from your account they have software that looks for keywords and other info they can use to target advertising at you.
It's the same thing with Google. If you use Gmail or the Chrome browser it is monitoring your emails, web surfing, and Instant Messaging for information. SO if you search the web for say, a new laptop, you will get ads for laptops from various laptop manufacturers that advertise with Google.
Other social websites do the same thing. Your life is an open book to them, and the more information you give them or send others, the more they can target advertising towards you.Kinda scary, huh.
Also know that various government agencies and large corporations also monitor social websites for whoever posts their private information publicly.
A Federal court just ruled that you as a person can have no expectation of privacy on the internet, as the information goes through third party servers, (your ISP) and if it's not encrypted then anyone can access legally.