Look up how many times a forced Windows update borked someone out of their computer.

Installing Windows without a key is not exactly straightforward, then there's that constant gentle reminder of how your copy of "Windows is not activated".

Microsoft COULD push an update that encrypts your hard drive, and forces you to pay $1000 for a key, if they wanted to.

It's unlikely, but the same as

> If Apple decides it won't work, you're at their mercy.