I take issue with the math on this one, I do not disagree that one person could purchase four controllers but I have a problem with the 1M being the number of people capable of playing. Pedantic, yes, but even if you assume dual-weilding for each user that would be a low of 2M capable of playing. I'm certainly not positing that a 1M sold-through equals 1M individual homes but it is possible though highly improbable.
I don't take issue with the rest of your post.
I mean 1m for buying games.
Your right 2 people can play on a ps3 with 4 controllers. But only 1 game needs to be bought.
User bases are important for developers esp early on in a hardwares life. Its easy to figure out how many kinect users and wii users are out there purchasing software. The picture isn't as clear cut with move.
btw i'm not saying i know anything about the move's install base. I'm just saying there are multiple ways to come across owning a move.
Hell I bought a move controller simply cause I have an eye toy already. My buddy already has 4 move remotes however. So i can see the spectrum and it makes for a much more confusing picture compared to the others.