HT to the Points Ninja for pointing this out
If you are planning on staying at a Hilton property, you can get 4x extra Membership Reward points per dollar when you spend $175 or more at select US Hilton properties from 11/1/13 to 1/31/14. You must first register any Amex card that earns MR points here.
The cities that are participating in the promotion are Atlanta, Baltimore, Chicago, Ft. Lauderdale, Hawaii, Houston, Miami, New Orleans, New York, Orlando, Phoenix, San Diego, San Francisco, and Washington, D.C. To see a list of the participating hotels, see the list here.
A maximum of 10,000 bonus points can be earned with this promotion.
The Points Ninja stated that “This offer might combine nicely with the Tripadvisor $50 off $250 Amex Travel Sync offer. ” however, the T&C of the 4x promotion does not apply to 3rd party merchants so this promotion would not be stacked together but it does seem like a great promotion!