Hmmm....

The MR Terms and Conditions (#6 under "Earning Points" seem to make it clear:

• No other person except the member may earn points for his/her account.

There are no listed exceptions for spouses. Still, there have been numerous reports on this board of successful attempts - intentional and inadvertent - to circumvent this rule.

Points from one spouse's account can be combined with those of the other for purposes of claiming an award. Thus, the only reason I can see to use the other spouse's account number upon check-in is to obtain a benefit that would not otherwise be available - such as an upgrade or getting to a higher elite level through more nights at Marriott. That would seem to border on fraud and runs the risk, however small, that Marriott might invoke General Membership Rule #9:

• In the case of fraud or abuse involving Marriott Rewards, point credit, mileage credit, reward use, or a participating hotel, Marriott and its travel partners have the right to take appropriate administrative and/or legal action, and all frequent flyer miles or points and certificates earned through Marriott Rewards may be forfeited and the account closed.