When you register at Dropbox, it initially provided 2GB of storage space. This is the moment when you feel cheated as the commitment was of 50GB.
There is nothing to worry as you can avail 50GB Dropbox space after logging in your dropbox account and completing some simple steps.
click on the image to re-size
Once you are logged in your Dropbox account, go to "get started" option.
You will find various options which will help you to gain 50GB space. Just complete any 5 steps and you will avail 50GB Dropbox instantly.
You can get more than 50GB on inviting your friends to join Dropbox.
Note: The account validity is of two years only. The method of getting the 50GB of space may change anytime.
Hope this helps!