Wonder if this will build up on the free space I already got. Dropbox was (is?) running a promotion where you got free space depending on how many people you referred and signed up. Google was also running a promotion on AdWords where you got like $100 free for signing up for an AdWords account. So I signed up for AdWords and then ran an ad for awhile that pointed to my Dropbox referral link. Got like 5 GB free this way. Well, it was $100 in credit, but nothing out of my pocket.