Also: Imagine GreaseMonkey scripts using S3 as a universal configuration pool and long-term data store. (The configuration pool idea, by the way, came from Dave Winer.)
We’ve talked in the past about offline data storage, whether via Flash or future browser enhancements. Holding data in the user’s own third-party store is a third option for storage, an alternative to conventional online storage as well as offline storage that allows the user to control their own data without having to maintain it locally.
The service is ideal for Client-SOA apps, where the browser runs the entire UI and makes REST or RPC calls to the server, which responds with raw data. The app itself could presumably load from another URL, your local hard drive, a bookmarklet, or a plugin/extension/GM script (with varying levels of security risk involved).
Of course, since my demo wiki is sitting in an S3 bucket with a public-write ACL, everythingâ€™s open to vandalism and subversion (of the bad variety)- documents and application both. S3Ajax does allow authentication through your S3 credentials, though, so a private group with restrictive S3 ACLs could use this wiki successfully.
Documentation on the S3 library is currently limited, but you can read more about the S3 Ajax Wiki here.
Update: As mentioned in the comments below, there’s also a new online API, Filicio.us, that lets you access your own S3 file store from the browser. Right now, the Filicio.us service acts as a proxy, but it looks like they have plans for direct access to S3 in the future.