I'm actually with Ubi on this 100%. I actually expected this kind of system to pop up years ago. Because if this works it could stop piracy, and that means finally more real PC games. Let's get some facts straight here:
Every single person with a capable gaming PC has an internet connection, so no problem there.
Games like WoW require you to be online to play aswell, and nobody complaints there.
Because let's face it, piracy has gone over the top. We al saw the estimates from bittorent from last year and that was just a fraction of the problem. Again don't blame this on Ubisoft, blame it on the people pirating games!
I really think we've reached a threshold here, and there are only two options left for alot of game developers: Get this or a similair system to try and stop piracy, or mostly abandon PC gaming.
As has already been said, no one has proven there is a negative impact from piracy and the reason they haven't is because they can't. If they could, they would. Statistical data on piracy would be everywhere, the math would be testable, and the results would be reproducable. The fact is, though, that piracy has a statistically insignificant impact on their business. Most people who pirate would love it if they could afford to buy legitimate copies, they don't because they can't.
Do take note, that they are also using this system to stop used sales. What they are doing is fighting tooth and nail to show some kind of improved profit margin. They do not care if you buy their game legitimately or not, they care if they get the money for it. They hate used sales just as much as piracy and this is a mover to fight used sales just as much as it is to fight piracy.
If they get their way they actually won't have any impact on pirates, since the game can be hacked to avoid the security altogether, but it will have a severe impact on people who buy games second-hand. What they are really doing is squeezing the middle market, which will only have the effect of making used buyers in to new buyers or pirates. This is not something that deserves praise.
Hell, the fact that people actually think this move is about piracy is laughable. They can't kill piracy, they know it, and you'd have to be completely naive to think this will slow the pirates down even one bit. This is about the used market, and you're going to miss it when it is gone. Trust me.