For some reason, I've been checked into already occupied rooms more often -- not that it's all that often for me -- with Marriott hotels than with other major brand hotel; even otherwise, I run into this happening with Marriott hotels more often than other hotels. Marriott hotels are of course very many and the loyalty program membership rolls are huge, but could this also be a function of how Marriott reservations are pulled up by the hotel front-desk even when they are using photo ID to pull up the reservations?