According to Marriott's phone recording there is a 50,000 points transfer limit per year a $10 fee per transfer.
I wanted transfer 81,000 from my wife's account to mine.
The Rep said he needed to talk to my wife to do the transfer and I said she wasn't available. When I switched to my falsetto voice he chuckled and said OK and proceeded with the transaction.
Not only did he transfer the entire 81,000 (he said it was now 100,000) he didn't charge me the $10.
I'll take that as a good sign of decent customer service.