Fair point but then again given US have just setup a gift registry service obviously they both think people will AND accept it's a valid thing to do. Apart from the buying lots of points and then onselling scenario would think US would think US would have a hard time justifying cancelling accounts because people are doing something they have just encouraged. Must admit I think it's a strange way of doing business too but happy to take advantage.
The registry may be a valid way to amass plenty of points fast and still within the spirit of the program. Some folks might even use the registry for its purpose, like a proper points registry in lieu of say a David Jones registry. But the potential issue that can arise is when folks start redeeming flights for other passengers who do not share the same surname, or even home address.
So if I, Mr. Legal, accumulates 2M points, and starts redeeming them for Mr. Doctor, Mr. Dentist, and Mr. Product Manager, then potential warning bells might pop up at US. US might even think I'm conducting a business where I buy loads of points under promo, and then on-selling it to those who I am redeeming points for and making a profit. Imagine how simple it could be to say to someone, give me $4K and I'll get you to Europe in First Class, and make $1.5k profit per person. It's possible. Some have even gone further and ripped customers off, see this article
here.
Cancellation of accounts may be a rare case, but its possible, so best practice would dictate that you stay within the rules, redeem each passengers flights from their own account, unless you can show you are part of a family, same surname, address etc.
