After Dropbox, its now Ubuntu One's turn to run a referral program to increase users and give the users a chance to get more storage. Now invite your friends and family members and get 500 mB extra storage for each successful registration.
All you need to do is to sign in Ubuntu One's web dashboard and grab a referral link. Send this link via email, Facebook or Twitter to your buddies and relatives and gain 500 mB of extra storage per registration. You can add upto 40 friends in Ubuntu Once, thus 20 gB of storage for free.
Also each member who joins Ubuntu One via referral link will get 500 mB extra, i.e. 5.5 gB of free cloud space.
So get started by logging in to Ubuntu One here.