Apple's retail site mentions a new Nike-Apple promotion:
Express. Define. Create. State.
Express yourself, define who you are, be creative and make a statement. What do your shoes say about you? That youre a fan of USC? That you adore the color pink? With NIKE iD, you can personalize your shoes to represent you. Visit an Apple Store and ask a Mac Specialist for more details about NIKE iD.
According to one report sent to MacRumors, Apple Store employees will be wearing the Nike ID shoes in stores along with Nike tie ins (Nike website as default on Safari) in a cross promotion effort lasting until May 18th.
Nike ID shoes allow you to customize your own shoes.
Update: Blurb removed from Apple's retail site.