That link gives you the answer you seek. It's an officially endorsed D3 mouse with the exact same functionality as the OP's mouse along with the 100 other threads about keyboards, etc., on this very same topic. Since D3 is a registered trademark of Blizzard and the only way you that mouse could exist, without current litigation against the makers, is if Blizzard signed off on it, and by doing so, Blizzard profiting off every unit sold. If Blizzard started banning people for using their officially endorsed product, along with it's functionality, which is its main selling point, they could open themselves up to a major lawsuit, regardless what the ToS/EULA states, since by endorsing such a product, while at the same time considering it in violation, would create a catch-22 and essentially nullify the contract. The only way it could result in a ban is if it were able to detect for you when to switch the gear and do so, which it can't. It requires an action initiated by you. Now some people will tell you that it automates blah blah blah. Well if they read the TOS the will find that Blizzard defines automatization as botting or in other words, the game playing itself, which again none of these products do.
Edited by Wickedness#1448 on 19/06/2012 00:15 BST