You must have an android device for this to work!
As found on : http://forum.xda-developers.com/show....php?t=1550699 and HotUkDeals
Linky : http://dl.dropbox.com/u/5152607/Drop...v2_theos0o.apk
Step 1: If you already have Dropbox installed on your Android device, you must Clear data, Force close and finally uninstall it from Settings > Applications > Manage Applications > Dropbox.
Step 2: Download and install the Dropbox+23GB APK Be sure to enable Unknown sources under Settings > Applications or Settings > Security (on ICS) before installing the APK!
Step 3: Launch the app as usual and log in.
Step 4: Wait for the confirmation email.
The confirmation email can take up to 30 mins
From what i understand the space is valid for 2 years afterwards you go back down to whatever space you had before. Also, the 23GB is added to whatever capacity you currently have eg If you have 4GB now you will have 27GB afterwards.
Also, once i got notification i was able to uninstall this dropbox app and install the market one.