Denny's First 500,000 Get Free Burger and Fries

I was just on Facebook and saw an update from Denny's stating that the first 500,000 to sign up for Denny's Rewards get a coupon for a free burger and fries coupon via email on February 28th. Don't know how many are left, but they said that there are still some left. Sign up here before it's too late.