We all are aware of DropBox, the popular cloud based service which allows you host your files on server and then you can access them from almost any where of the world using computers or mobile phone. Your all files are sync with all devices which you add.

Dropbox provides 2 GB of space free to its users and when you invite any of your friend they provide you some more free space, now they had doubled the referral space and if you are a free user then you will get 500 MB of data free.

In this way you can get at most 16 GB for free, its good if you are not paying a single penny, on the other hand if you area Pro account user then you will get 1 GB free on each referral and in this way you can earn atmost 32 GB.