I had to travel recently, so I took a laptop with clean Windows 8.1 Pro install.
At my destination, I've purchased a SIM (they only had 1GB data packages) and put it into the 3G/wifi router I carry.
I powered the laptop, connected to Internet via said router, checked few things, then went away for few hours.
When I got back to apartment, my data package (and Internet connectivity) was killed because Microsoft idiots decided to start downloading Windows 10 even though I have explicitly closed/rejected all the 'offers'.
Those retards did not take into account the possibility that not everyone running Windows is on unlimited broadband data package. Great planning there.
At home I did a plain install of 8.1 on another computer, and same thing happened - even though I explicitly rejected everything related to Windows 10, idiots made it so download starts anyway. I had to 'hide' the Windows 10 in Windows Update in order to stop it from being downloaded.