Topic: Can I keep my extra free bonus space when I pay to upgrade my account?

Yes!  All bonus space that you have earned is yours to keep even when you upgrade your account to 25, 100 or  500 GB.

Example:

You start off with a free 3 GB account. 
Then your refer friends to CloudMe and earn 16 GB of free bonus space.
So now you have 19 GB of free space on your account.
When you upgrade to say 25 GB, the total space on your account will be 41 GB.  (of which 16 GB is your earned bonus space)

Your bonus space is yours to keep no matter what size account you have to begin with nor what size account you upgrade to.

Enjoy your extra bonus space!