Amazon and Facebook have clearly been on the leading edge of two forces driving the web as platform - cloud computing and exploitation of the social graph. Now these two companies have announced a partnership that lets Facebook developers leverage both innovations by giving developers a path to employ the Amazon cloud computing model based on the EC2 and S3 APIs. This has the ability to provide an infrastructure for developers who dream of building a wildly viral Facebook application and worry about how to handle the growth.
Amazon's EC2 provides the metered compute capacity for creating virtual instances, and S3 the storage component. The partnership with Facebook doesn't extend either of their respective APIs, but it offers a a set of resources including a step-by-step process to launch a Facebook app using the Amazon platform.
Facebook developers had already one solid option with one-year-free hosting from Joyent which partnered with Facebook in December and it's likely we'll see a variety of such app infrastructure services appearing in the next few months.