More on topic, Windows 10 comes with the following new "features":
Keylogger. Everything you type into your keyboard is recorded. Everything. Emails, passwords, credit card numbers, diary, that dirty novel you secretly work on, all of it. Imagine if someone was able to get past the security of windows (which happens constantly) and access this keylogger. Or intercept the sending of its contents to Microsoft. Or even if not, do you trust random Microsoft employees with EVERYTHING you ever type into a keyboard?
Voice Recognition. AKA: Recording everything you say. Microsoft specifically reserves the right to send recordings of things you say to their servers.
Data Collection. More of the same really. Your contacts (from all services you use), Calendar events, speech patterns, handwriting patterns (incl. your signature), web history, etc etc etc.
Use Info. If you open a file it records the name of file, metadata about the file, what program(s) you used to open the file, how long you spent using it, etc.
Forced Updates. No option to turn them off in the Home version at all. In fact, Windows uses YOUR BANDWIDTH to upload updates to other Windows users. Sort of like the BitTorrent network but without the ability to limit the usage. Try to play an online game with THAT shit going on. Oh and did I mention you don't get to disagree or have any say whatsoever in what changes these updates make? Or the fact that since you get a lot of it from other Windows users rather than directly from Microsoft, it opens the possibility to "poison the water" and incorporate malware into the update? I mean, hopefully the update program would use something like CRC to check the integrity but with Microsoft it's a bad idea to give them the benefit of the doubt in such matters.
Advertisements in the Start Menu. Yup, really.
WIFI sharing. Anyone visiting your house with a Windows 10 device and a skype or outlook (or even Facebook if the option is on) account, shares your Wifi password with Microsoft. Possibly even with their contacts, though I'm a bit fuzzy on this detail.
Full access to your computer by Microsoft at any time. Yup, really.
There's more but yeah, this is pretty much full-on dont-give-a-fuck maximum surveillance-mode OS. Friends don't let friends get anywhere near Windows 10.
Also everybody should stay the hell away from Facebook and Reddit and Google.
Or, come up with a usage strategy and strictly adhere to it. The high-effort way to deal with it is to simply carefully think your way through every click, every typed character, and every anything at all you do anywhere on your computer at all times with absolutely no fuckups or weak moments or drunk browsing ever. The much easier way is to take precautions from the start. Like using an amnesiac OS (Faust suggested Tails, which is both amnesiac and a great suggestion), or living off of a LiveCD or other setup where the OS is running from read-only media, etc.
That doesn't solve the internet side of the problem though, to solve that I recommend a VPN and Tor and even THEN staying careful with what you're doing. Some might call these measures extreme but measures this far are only necessary because the insidious prevalence of data mining has become so extreme.
Wearing body armor and riot gear seems extreme when you look outside your window and see a suburb, but definitely not so when machine gun bullets are flying at you. Make no mistake, my friends, on the issue of privacy we are most definitely under fire and the rate of fire is quite high.
Edited to add:
I almost forgot the most nifty part about the new features of Windows 10. If you turn them off, they have a "mysterious" tendency to turn themselves back on after awhile. Seriously. They really do that.
(and by "mysterious" I mean that Microsoft freely admits that happens and they designed it that way)
