Nobody has to pay but those willing to because they want to help out in the costs of the server and the time it takes Mickey programming, should perhaps get a little advantage.
I heard everybody write here about making it tough to get nukes.
Well...becoming a donor to get nukes is a great idea i think.
Putting 'donor' between tags in the player list and forum is a good way of showing who actually paid.
And Mickey's idea of speeding up the armies.
And I do think for big payers there could be a reward like gold mines or something.
This way, for non payers there would change almost nothing.
Only the nukes.