Originally Posted by iff
It's for people working or residing in Ile de France, not for visitors, though I suppose if a visitor wanted to fill out the form with a Paris address and phone number, they would probably be able to get one.
The Carte Orange is also intended for people working or residing in Ile de France (because it's subsidized by the government), though they usually will sell it to anyone who requests it.
It's probably easiest for most people to stick with the Carte Orange, which won't be disappearing anytime soon.
I think (but am not positive) that the Navigo must be mailed to the address that has been given. We just used a Paris Visite last week because we arrived in Paris on Thursday and were too late to buy the Carte Orange. It's more expensive than the CO, but works just as well. It includes the Noctilien night bus and the Balabus too. We use buses a lot so it paid for us to buy the Visite.