Via this Flyertalk thread. Complete a very quick survey about your social media habits and earn 1,000 Starwood Preferred Guest Starpoints! You must complete the survey by March 9, 2012. Starpoints will be credited to your account within 30 business days. Employees of Starwood Hotels and Resorts are not eligible.
Most importantly, remember to enter your name, email address, and Starwood Preferred Guest account number in the last box of the survey! If you fail to enter your information, you will not receive the Starpoints.
EDIT: Wow, that went unbelievably fast. The survey is already closed, I'm guessing because it went viral and Starwood Preferred Guest quickly realized they'd be losing a lot of Starpoints on this!