Sure it...works...just that by the time you are forced to use a phone activation, chances are you WILL have to talk to somebody, because they want to ask you how many PC's you have it installed on, because it's already been activated past their threshold (and by the way, it doesn't matter whether or not you tell them the truth - I guess they just assume that you'd much easier lie to a computer than a person.) And even then, that is only after you've tried and failed twice to enter a long string of numbers, which takes several minutes, and then you have to repeat the process YET AGAIN with that person instead of the automated system. About half of the time I've done this, I've had to actually give the numbers to two different people, with the first one giving me the activation key twice only to have it fail twice after saying the key is good. In the end you can very well have to go through giving the other side the installation ID 5 times, and having to wait for them to read the activation key to you 3 times. And that's not even counting the time you wait on hold, which ads yet more time.
I went through exactly that the time I most recently installed Windows 8, by the way, and it wasn't even due to multiple activations, rather the activation scheme didn't like the way I used an upgrade key to install a fresh copy, and then added Windows Media Center on top of it. I think I was on the phone a good 40 minutes.
It's so annoying, I hate it. Windows 7 I no longer bother to even use my legitimate keys (I own even more copies than I actually use,) I simply run Daz's pirate loader and be done with it - it's so much easier that way. I'd love it if they made a similar loader for Windows 8.