A while back I jumped on the wireless charging movement when I picked up a Powermat for my HTC EVO 4G. This little mat let me conveniently set the phone on its surface and it would charge it right up. I didn't have to try and finagle the little microUSB connector to charge the phone; just set it down and walk away. This was hands-down the most useful smartphone accessory I have ever owned.
Why don't tablet makers incorporate wireless charging into the case like HP and the TouchPad? I don't think it would take up that much space/bulk, and probably wouldn't add much to production costs. Those costs would be recovered by selling wireless charging stands/docks anyway.
Wireless charging for phones and tablets doesn't seem like a big convenience until you experience it firsthand. There is something liberating every time you set the gadget on the mat or dock. You don't have to fuss with those connectors, and you don't have make sure the device is really charging. You simply place the tablet on the stand and leave it alone.
Tablet makers are scrambling to set their device apart from the crowd, and this feature would certainly do that. I believe a good implementation of wireless charging on a tablet would be well received by the market. This potential is unrealized, waiting for some smart company to jump on it.