I know a couple of people who do this successfully. Both have the same name though. My father in law and brother in law (same name, so they share all frequent flyer and hotel accounts). I also have a friend who's son has the same name and they share their accounts without any problem.

Personally, it would be great for me, as both my wife and I are HH Diamond and make it on stays and nights. It would be great if it were just one account, instead of accumulating points into two different accounts. Hers looks much larger as the surpass points go to her account, not mine.