If you are an App Store developer, then you can now create a sweepstakes campaign around your application. Apple has added the following statement to their terms of service for the App Store:
“3.3.17 Your Application may include promotional sweepstake or contest functionality provided that You are the sole sponsor of the promotion and that You and Your Application comply with any applicable laws”
One of the first applications to support a sweepstakes campaign around the application is called the Ka-Ching button. The Ka-Ching button allows you to win a $1,000 prize by downloading the app and simply pressing a button. [ZDNet]