RPS: Firstly, the obvious. Why free to play? Why now?STOP!
Declan O’Connell: Subscription-access greatly limits the potential player-base of a game. You’re making money off of every player who is willing to pay $15 a month, but you don’t get those players who would play if it was $10 or $5 a month, or those who would pay piecemeal for things that grab their interest. You also only make $15 per account for which your hardcore players can find a use, when they might pay even more for extra features. That’s the money end.
Read no further. That is why F2P works as a business model. It removes the barrier to entry and allows players to participate at any investment level. Proper game design can then go a long way to encouraging players to spend more at the same time making sure players that don't spend as much don't feel left out.