A story is making the rounds about the potential security and/or privacy risk caused by the fact that if you use Windows 10's built-in disk encryption, the encryption key may be send to Microsoft's servers. ARS Technica explains the ordeal and provides details on how to get a new key over here.
It may be true that Microsoft has the decryption keys to your encrypted hard disk if you bought a PC with Windows 10 or Windows 8.1 preinstalled, and if it supports device encryption (we still come across machines that for one reason or another don't support it, or need reconfiguration to support it), and if you use a Microsoft account to log into Windows. But it isn't a security disaster that they do, and if you aren't happy that they do, it takes no more than a couple of minutes to delete the copy of the key they hold, and then update your system to render their key useless. This can be done on any Windows version, even Home.