Amazon S3 is designed to provide cheap web data storage for developers.
Amazon S3 provides a simple web services interface that can be used to store and retrieve any amount of data, at any time, from anywhere on the web. It gives any developer access to the same highly scalable, reliable, fast, inexpensive data storage infrastructure that Amazon uses to run its own global network of web sites. The service aims to maximize benefits of scale and to pass those benefits on to developers.
Authentication mechanisms ensure that data is kept secure and uses standards-based REST and SOAP interfaces designed to work with any Internet-development toolkit. All this for a cheap $0.15 per GB-Month of storage used / $0.20 per GB of data transferred.