<font face="Verdana, Arial, Helvetica, sans-serif" size="2">Presuming properties pay 10% of room rate to travel agencies as a booking commission, this could be Starwood's attempt to reduce the number of rooms that require a 10% (or x%) commission and thus increase the margins.</font>
If you go through your corporate agency there is a good chance that your corporation (if large) has negotiated a "net of commissions" rate for the hotel. Then the hotel is just required to pay the GDS fee.