UPDATE: Apple has changed the rules of the contest and now includes this line:

Photographers who shoot the final 10 winning photos will receive a licensing fee for use of such photos on billboards and other Apple marketing channels.

Apple:

Apple is kicking off the year by celebrating the most stunning photographs captured on iPhone, the world’s most popular camera, by inviting iPhone users to submit their best shots. From January 22 to February 7, Apple is looking for outstanding photographs for a Shot on iPhone Challenge. A panel of judges will review worldwide submissions and select 10 winning photos, to be announced in February. The winning photos will be featured on billboards in select cities, Apple retail stores and online.

Post your best photo taken on iPhone to Instagram or Twitter with the #ShotOniPhone hashtag to participate in the Shot on iPhone Challenge.

Keep in mind that, like many contests like this, Apple won’t necessarily pay you if your submission is accepted as a contest winner. That being said, it can’t hurt to tag your photos to enter the contest.