It's a new way to help let your info-products go viral.
From the site:
In today's world the value of people talking about your product is sometimes higher than the money you would get for it. 'Pay with a Tweet' is the first social payment system, where people pay with the value of their social network.
It's simple, every time somebody pays with a tweet, he or she tells all their friends about the product. Boom.
Pay with a Tweet - A social payment system