Yes, that's in T&C's:

4B.4. An “Eligible Rate” is the rate you pay for your room, but excludes:

(a) for hotels located in Asia Pacific*, rooms where the booking is not made directly with Starwood or a Starwood branded web-site;

(b) for hotels located outside of Asia Pacific*, pre-paid rooms where the booking is made by an agent or third party and you pay for that booking directly to such third party, such as tour operators, and pre-paid channels, including, but not limited to priceline.com, expedia.com, hotels.com, hrn.com, hotwire.com, lastminute.com, site59.com, orbitz.com, travelocity.com, cheaptickets.com, quickbook.com, travelweb.com, lodging.com, yahootravel.com, and travel.msn.com;

(c) room rates for group commercial or group leisure bookings where rooms are booked as part of a conference or organized tour that is either master billed or paid at tour operator rates or where the bookings for six or more rooms are linked;

(d) room rates that are master billed or paid at tour operator rates, wholesaler rates, including WFNR, TAED rates, and crew room rates;

(e) employee rates;

(f) complimentary rooms (including, but not limited to, any Free Night Awards earned through the Program or otherwise) and other rooms reserved using Starpoints, including, rooms through the Program’s Cash and Points Award room rate.

Regarding elite member benefits and ineligible rates:

4C.6. Except for hotels located in Asia Pacific*, Platinum Members are not eligible for any in-hotel benefits when booking pre-paid rates through pre-paid channels, such as, but not limited to the channels listed in the definition of Eligible Rate; however Platinum Members will earn Starpoints on Eligible Charges made during the stay. Since these prepaid rates do not meet the definition of an Eligible Rate, no Starpoints will be earned on the pre-paid rates and these nights to not count as Eligible Nights when calculating the Platinum Minimum Requirements.

*Asia Pacific means hotels located in: Australia, Bangladesh, Brunei, Cambodia, China (including Hong Kong and Macau), Fiji, Guam, India, Indonesia, Japan, Korea, Malaysia, Maldives, Nepal, New Caledonia, Singapore, Taiwan, Thailand, Vanuatu and Vietnam.

Also...

5.3 (a) room charges that are not included in the definition of Eligible Rates (NOTE: certain pre-paid rooms where the booking is made through a third party are not Eligible Rates);...

Right now, there is a Q1 promotion going on that would net an additional 500 Starpoints per night on eligible nights within a stay, so I would at least try and find out if a booking on United.com would net more airline miles than Starpoints, realizing that transfers to United Airlines Mileage Plus are done at 2 Starpoints to 1 airline mile unless done through the Direct Deposit option, where it is 1:1.

Best regards,

William R. Sanders
Online Guest Feedback Coordinator
Starwood Hotels & Resorts Worldwide

[email protected]