Knock it all you want, ldsant! I decided to tackle this one!

I was quite surprised to see how many Starwood reservation and cancellation emails I have in my email account. It was very easy to pull up my history of email confirmations.

The 3rd and 4th digits help reveal a pattern. All of my reservations in the past year demonstrate this...
xx32xxxxx = booked on Starwood website
xx75xxxxx = booked by phone through Plat Concierge

Somewhere right around January 23, 2007, the website reservation numbers rolled over from xx31xxxxx. I have to go way back to 2003 to see xx30xxxxx.

I had one conf number in 2007 that started with a zero. I have a number of 8-digit conf numbers from past years that appear to have had their leading zero dropped -- at least that's my assumption from the email confirmations.

Back in April 2006, I booked two completely separate reservations for completely different dates at the Aladdin. The reservations were booked 3 minutes apart. Only the first two digits were different, so that tells you something about the sequences, doesn't it?

One day in June 2005, I was particularly busy. I booked 3 reservations within 10 minutes that all had the same final 7 digits. About 7 hours later, I booked 2 reservations within 8 minutes, and their final 7 digits matched each other.

(Hmm. I see one more in March 2006. I'm seeing another pattern: when a sale rate popped up at the Aladdin, I booked multiple reservations.)

In each of the above cases, the first two digits increased for the newer reservation.

So here's what I suspect happens:
A 9 digit sequence number is generated. The last two digits are taken off and put in front. I'll guess that the phone and web reservation systems have some separate components and that that's probably why they create reservation numbers from separate sequences.

I am not sure about res numbers from 3rd-party reservations or packages. Anyone know? (Other than SL II? )

Though some companies choose incorporate a check digit into confirmation numbers, I don't think that's the case here. If there is one, I'd argue that it would have to be the second digit.

(If I show up dead within the next week for any cause other than that of skiing off a cliff in the Vail Valley, prime suspect number 1 has posted to this forum.)