Considering the onerous Windows registration process, Microsoft is apparently not contradicting any privacy laws around the world, nor are they forced to make their users sign multiple agreements. That issue simply cannot be a valid.
I believe Mark Shuttleworth was quoted having said over three years ago that ".. about 1% of all computer users use Ubuntu". That figure is still being used by various product developers as an excuse for not providing Linux support for their product. To add insult to injury, the fact that the number is so old, is used to argue that Ubuntu growth is stalled and not going anywhere. Whatever the real number is, it can't possibly be that low anymore, three years later. If Mark cannot come up with a more up-to-date number, who can? Seriously!
I think it would be both silly and self-destructive to continue bury our heads in the sand and not measure it for fear of seeing a low number. If we don't measure the true population, how on earth will we ever know when we are successful? When can we have a party because we are successful and not just because we wish we were? Any claim of success falls flat in it's face without some measure to back it up. Let's not allow the lack of book keeping become the evil that kills our success, please.
It is rather disheartening to have actively promoted Ubuntu for years with absolutely nothing to show for it, no way of showing whether we have ever made any positive difference or whether it has been worth our while.
Why does Canonical need those numbers? Exactly because they have no money for marketing Ubuntu. If not for any other reason, to give us some motivation to continue marketing and "sales" at our own expense, at our time, on behalf of and to Canonical's benefit. Don't make it so damn hard to help you.