> this is also true of the reservation itself...
Too true. If you have a normal reservation (vs some kind of pre-paid room), they oversell their capacity based on a statistical model. This means if everyone with a reservation shows up, some of the last to check in won't have a room (which tends to occur during statistically unusual events like a large trade show, where every reservation is more likely to show up). The hotel will basically just say "sorry" and suggest another hotel which may have rooms. I think they try to recommend hotels that are nearby and similar but sometimes that either doesn't exist or is also sold-out.
One of the benefits of having platinum status at Marriott is they'll actually guarantee your room but platinum status isn't easy to get. I used to frequently drive into the bay area late at night to avoid traffic, arriving at the hotel at midnight or later. Being platinum at the time, I'd sometimes get a call on my mobile from the manager after 9p to find out if I was showing up for sure and I'd tell them "Yep, I'm driving now." That's how I knew they were sold out and bouncing people with reservations. They didn't want to keep holding my room if I wasn't going to show up (being platinum there was no penalty for no-showing on a reservation).
A tip: if you have a non-guaranteed reservation and you think the hotel is likely to be full but you're arriving later in the evening - call the actual hotel front desk before 5p (not the reservation center), ask to speak to the manager on duty and ask them to check you into your room over the phone. Ask for the actual room # and then have them actually print out your card key and put it in an envelope under your name at the front desk. Once your reservation has been checked in, a room assigned and a key printed, it can't be given away by the late shift.
