That whole 'refer a friend' thing must be working. Or maybe it isn't. Either way, Dropbox has felt the need to double the extra capacity you get as a reward for persuading your buddies that cloud storage really is 153x better than a USB stick. For each successful referral, you'll now get 500MB up to a maximum of 16GB. Pro users will get 1GB per referral up to a limit of 32GB. Get in there quick before someone else in your gang starts promoting Google Drive and its rumored document editing capabilities.