The world’s largest Internet retailer has just started selling product directly through the world’s most popular website – meaning that now, thanks to Amazon, we will get our first real read on the potential that Facebook possesses as an e-commerce platform.

Amazon launched its first e-commerce storefront Friday on Facebook, which consists of a simple “Shop Now” tab on the Pampers Facebook page. Users can buy Pampers and other Procter & Gamble products directly through Amazon by going to the page and signing in with their Amazon accounts.

Thousands of retailers sell product on Facebook, but this is a first for Amazon and it could be very valuable in determining the viability and validity of social commerce as a platform. The iconic e-retailer has shown an increasing interest in Facebook in recent months (but who hasn’t), striking its first relationship in July in which it allowed users to connect their Amazon and Facebook accounts to generate product recommendations for their friends on the social network.

This latest partnership, however, encompasses direct selling through Facebook. E-commerce merchants are finally coming to accept the marketing potential that Facebook, its half a billion users and other social media present, but the widespread adoption of actually selling products on social networking sites is going to require some hard evidence to support it.

Perhaps that development took a step forward today, thanks to Amazon and, of all things, diapers.