well, those are indeed pretty draconian terms and conditions.

has anybody tried to use the Marketplace search system?

I just tried to search for "2 rooms, 5 guests" at the Marriott Chicago Magnificent Mile and I got the suspiciously low mileage rate of ~48k miles for two nights.

To double-check I tried "1 room 2 guests" and got the same mileage rate (~48k for 2 nights).

This makes me think the "number of rooms" feature does not work, and it actually shows one room only, so i wonder what would happen if I went ahead and reserve, would I only got one room?