The problem we've been having a lot lately are shady travel agents. They're booking VIPs who want non-smoking into the smoking bucket, and then not listing their HH numbers. So when the VIP shows up, we're in a major bind trying to find a non-smoking when a smoking reservation was made. A lot of the time we just can't do it, because the numbers don't add up, and we've already given the non-smoking away.
The other thing that happens a lot is a HH member with profile preferences that aren't their real prefs. If you say you prefer 2 doubles, for example, we may override your reservation to try to grant that, especailly if that makes our numbers add up better.
The moral of the story is, it's worth your time to take the confirmation number and call back over to the hotel in advance to make sure you can get what you want, and also to keep your profile updated and on every reservation.