How To Detect Who Is Online In Facebook?

What are Facebook, LinkedIn, and other social sites doing to aggressively detect who I am?

• And how can I protect my privacy, the privacy of my peers, and the integrity of my data? Today as an experiment I created a Facebook account using a new incognito window. In another normal window the only thing I had up was my Gmail. While going through the setup process Facebook knew things about me that were impossible to know - where I went to high school, home town, even suggested friends were in an order that suggested that were ranked by the number of people whom I most frequently contacted in email. Websites that I had visited in other windows were even auto-liked somehow. On LinkedIn I noticed that that site read my email despite me not having given permission. In fact, because of how aggressive LI has been in invading my privacy I've done whatever else I can to block the site. I also did not give Facebook any permissions to read my email or use my contact list in anyway. I have never clicked like on anything. How are companies like this using the information and data on my computer for their algorithms? How can I protect myself against it? Does no one else find this a little concerning? EDIT: I was going to add the following as a comment, but thought the questions therein would benefit being part of the question. I've read through their TOSs.  On each of these sign ups there is an option to "invite" or "import" contacts from address books. For all of these companies I've declined.  Those TOSs are long, so perhaps I missed it. To those who have read them, can you point out, in one for example, where it expressly states that even though I decline in those steps they can still  move forward with importing said contacts or reading data I've opted not to give them in that process without my knowledge and without my authorization?  And if I missed it because it's legalese, where would one be able to interpret that in said TOSs a clause (clauses) that grant the right to read data and contacts on my computer without my authorization and without me knowing it?

• Answer:

  The thing about social media and the internet in General is that every site has the right to collect and store your data. By signing up for a Facebook account, you are agreeing to their terms and conditions which clearly state that fact. Linkedin is the same. When you go on Google and search things, google also stores that information. As per their user agreement whether you have an account or not, by using their service (such as search) you are giving them permission to collect and store data. The only way to 100% avoid this is by not using the internet but, let's face it- in this day and age that is almost impossible. Facebook has settings accessible to control what other users have access to in terms of your information, as does linkedin and every social media site. Setting these to private prevents other users from seeing the information but it does not prevent The service (Facebook, Google, LinkedIn, etc.) from collecting and storing that data.