From FT:

I got a mailer from AMEX for my Starwood Card. No Promo code not sure if it is open to everyone or it is a targeted promo.

Spend anywhere between 8-15-07 and 9-15-07 and get the following bonus depending on the amount you spend.

$500-1000 = 25% bonus points
$1k-5k = 50% bonus points
$5k-10k = 75% bonus points
$10k-20k = 100% bonus points
$20k + = 200% bonus points.

Bonus in addition to normal earned points and SPG Bonus.

This is a sizzling offer for Starwood Amex cardholders, though I strongly suspect that the offer is targeted, as Amex rarely makes these promos available to everyone.