Follow-up question here:

When I log into my Dividend Miles account, it looks like I can change my name and contact information by clicking on "Tools" and "Account Information".

I am NOT advocating doing this, and I am not doing and will not do it, but what's to stop you from changing your own Dividend Miles info so that it matches someone else's name, etc. on the other person's ticket, then putting your Dividend Miles number on someone else's reservation and collecting miles from their flight? Surely US would catch that, right?