If you are building a web application that allows people to store documents and files, you might want to just outsource the storage! It’s a headache to maintain storage on your own server when the number of users grow. You have to worry about not only the speed of download but also the bandwidth used on your server. So it is wiser to use a third party service to store the files.
And it’s the age of APIs! If the storage provider gives easy to use APIs to store and access files, what better than that!
ProgrammableWeb has a roundup of 10 Online Storage APIs. Pick the one that suits you!