I see that the rewards for this program are for a limited time (extra 3GB for 2 years). Maybe they realized their free plan + referral space was too generous. I currently have 21.9GB for free on my Dropbox taking advantage of the 18GB of referrals you can get as well as the additional couple GB they give you if you use the "Camera Upload" feature.
If they gave all these students that 3GB permanently that might bring people up to some sweet spot where most of them wouldn't have a real need to pay for the service.
I wonder what they're going to do when the promotion time runs out. If they're going to delete or block access to a random 3 GB of data in someone's dropbox, they're going to be dealing with a lot of upset customers.
(Should these people be aware of the fact that their space is going to run out, and have up-to-date backups of their stuff? Obviously. But the hard fact of life is that people do use dropbox as their only backup, and if something goes wrong there, they're going to be a customer support headache.)
The way it currently works is that they just don't allow you to upload anything until you're below your limit. They continue to store whatever is there, and do not delete it.
I have DSL internet with a peak of around 60 KB/s up (thanks to the US telecom monopoly, my only other option is cable for around $80 a month with 300KB up). I couldn't saturate my drive, dropbox, and Ubuntu one accounts even if I wanted to.
I wonder what happens after the 2 years are over. If they deduct your limited 3GB and you are over your limit, will they just delete random files until you aren't over capacity anymore? Odd.
If they gave all these students that 3GB permanently that might bring people up to some sweet spot where most of them wouldn't have a real need to pay for the service.