1. Amazon s3,
http://aws.amazon.com/s3/
2. Amazon s3 documentation,
http://docs.aws.amazon.com/AmazonS3/latest/dev/ACLOverview.html
3. Box,
https://www.box.com/
4. Dropbox,
https://www.dropbox.com/
5. Dropbox number of users announcement,
http://techcrunch.com/2014/04/09/dropbox-hits-275m-users-and-launches-business-product-to-all/