Well there are actually benefits to not using a built-in battery. Some people like me have loads of Eneloops constantly charged that we can switch in at any time; no need to go wired when your controller suddenly loses charge while you're gaming. Also you don't have to toss your controller when a built in battery dies.
This adapter though, there are no upsides to this except that you have a dumb extra weight attached to your controller that does everything half-assed. Not to mention we are giving MS and whichever retailer this adapter sells at nearly pure profit. Building this POS into the controller adds negligible cost to the controller.
I don't want to sidetrack the discussion further but, so you know PS3 controller batteries are user replaceable and it's quite easy to do.
As for everything else, yeah I agree. This is a complete scam, although I do prefer the convenience of built in batteries though.
I guess I'd be more outraged if I hadn't already come to expect this kind of behavior out of the company. Frankly I'm surprised they didn't go the route of blocking out non licensed headphones for simultaneous game/chat audio.