When staying on Priceline stays you do not earn SPG points.
http://www.starwoodhotels.com/preferredguest/terms_conditions.html
See Section 4A.2
4A.2. Preferred Guests will earn 2 base Starpoints for each U.S. dollar or equivalent of all Eligible Charges incurred and paid for by the Member at Participating Properties. See Section 4B.4. for the complete definition of Eligible Charges, but
note that 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 or 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 msntravel.com are not Eligible Charges and do not earn Starpoints. Paid shall mean receipt of good funds. Accordingly, if you stop payment on a check, if a check bounces, or if you dispute a credit card bill, you have not paid and you will not earn Starpoints on that transaction.