Let's look at the T&C's:

" Transferring Points from One Account to Another

1.This member benefit is only available at time of reward redemption (only one reward request per redemption, please).


2. Immediately prior to redemption, a member may authorize the transfer of the necessary Marriott Rewards points into the spouse's Marriott Rewards account in order to qualify for a specific reward.


3. Only the Marriott Rewards points needed to redeem the specified reward, rounded to the nearest 1,000 points, may be transferred - not more or fewer.


4. An "Authorization to Transfer Points" form must be completed and submitted to Marriott Guest Services to transfer the points. Forms are available by calling Marriott Guest Services. A request for reward redemption from the transferee's spouse must be submitted to the Guest Services Center with the Authorization to Transfer Points form.


5. Once the authorization for transfer is received and processed, the transferee relinquishes all rights to the transferred points, and they become the spouse's points.


6. For all "stay" related promotions, a "hotel stay" or a "stay" is defined as all consecutive nights spent at Marriott by a Marriott Rewards member."

Seems to me it's pretty clear that this will work only between spouses' accounts. Not sure how they would interpret that for same sex couples, but it sure does seem to exclude transfers between strangers.