We need a service which allows you to sell something (documents,videos, ebooks, images, coupons, songs, audios, everything which could be trasformed in bits) via online store, into the service's site itself, via URL or embed code, to embed into a blog, a website, everywhere. The payment is made with a post on Facebook/Twitter, where there will be a short link to provide tracking and stats.
Paymention should use the API of Bit.ly to track each single url which will link the payment to the content.
It should be integrated with Facebook Connect and Twitter Oauth. The site should be built in a way it could be possible to easily build an iOS app to support it.