New info on this one...it's back and ongoing.
Verbally, I've learned that AmEx is again offering what they call a courtesy upgrade to Diamond to US Hilton HHonors Platinum AmEx card holders who have over $2,500 in monthly card spend over a consecutive six-month period. Ongoing through April 2006. Must be registered as a U.S. resident in the HHonors system. Info is based on conversations with supervisors at Amex and HHonors with an AmEx supervisor reading part of a memo outlining it all. According to the memo, card holders cannot spend $30,000 in one month and be selected; it has to be distributed over 6 months, and never less than $2,500 per month.
And they aren't calling it a promotion, but rather a courtesy upgrade. Few people at either Hilton or Amex are willing to talk to card holders about it and I wasn't allowed to get a copy of the memo. And she knew of nowhere else where this courtesy upgrade was mentioned. Very smoke-and-mirrors for some reason.