Previous poster's confirmation is misleading -- it does not appear to be mandatory. I just went through the process on my Windows 8 machine, and you can choose to save to the recovery key to a file or print it out in lieu of storing it with your Microsoft Account (http://imgur.com/J0zk6I5).
Two caveats:
(1) It's possible Microsoft could choose to store the keys online regardless of what the user picks, but it's certainly not their official stance.
(2) Microsoft does automatically store keys online if you're using "Device Encryption" in Windows 8.1 (http://arstechnica.com/information-technology/2013/10/window...). This uses Bitlocker code but is distinct from using Bitlocker itself though -- i.e. if you do a vanilla Bitlocker encryption, your system should not send the keys to MS without a user (or admin) explicitly telling it to.
Two caveats:
(1) It's possible Microsoft could choose to store the keys online regardless of what the user picks, but it's certainly not their official stance.
(2) Microsoft does automatically store keys online if you're using "Device Encryption" in Windows 8.1 (http://arstechnica.com/information-technology/2013/10/window...). This uses Bitlocker code but is distinct from using Bitlocker itself though -- i.e. if you do a vanilla Bitlocker encryption, your system should not send the keys to MS without a user (or admin) explicitly telling it to.