I personally think that a program would do better if it was targetted to
one country. For instance; you want outside advertisers, selling products that need to be sent via mail etc. so you have a US 'client database' for your US advertisers.
(USA just being an example; could be UK, NZ, whatever)
You may not have the amount of members you would have if it was open to all countries, but your chances of getting solid advertisers is greater, I think.
For instance, I cant make money from survey companies because my opinion as a South African rarely has any value to them. Fair enough, chances are I'm not going to buy their products and probably havent even heard of them!
If you want your program to run along the lines that the majority of ptr's are now, targetting people who can speak English rather than along geographical lines (not many 'solid, shippable' products being advertised) then I would open it to all countries.
Did I make any sense here?
Of course, if all programs had to go this way then I would be out. Just my opinion on what I think would work.