Why use Amazon S3? Here are some arguments for using S3:
S3 is potentially cheaper than the alternative solutions. For instance, Don MacAskill, of SmugMug, a photo-hosting service akin to Flickr, estimated that SmugMug saved about $692,000 in 2006 by using S3 instead of buying and maintaining the equivalent amount of storage.[261][262]
S3 promises high scalability, both in volume and in the rate of change of storage needs. You “pay as you go” and pay for what you use. That means you don’t have to invest up front in buying the maximum amount of storage you think you will need. The utility model lowers the barrier of entry to the level that a relatively poor individual can afford to create a Web 2.0 application.
Robustness is part of the picture since Amazon.com claims it runs its own infrastructure on S3, and therefore you can expect reliability similar to that of Amazon.com itself.[263]
For specific examples of how S3 is being used, see the following:
http://jeremy.zawodny.com/blog/archives/007641.html for a list of backup services and tools that use S3
http://solutions.amazonwebservices.com/connect/kbcategory.jspa?categoryID=66 to see the solutions that developers have already built
Because online storage is accessed through the Internet, latency (and how it will affect your application) is an important factor to consider when looking at S3 and similar services.