Well, they'll be able to sell them, trade them on exchanges, but I won't be promoting that. It'll be used as an in-game currency. If people want to list it on exchanges, buy/sell it, that's up to them, but the game will determine the value of the currency more than the markets will.
I'm not closing off the ability to withdraw the currency. That's part of the appeal. As it's an in-game currency it will be used to buy/sell "items" within the game. So you'll be able to deposit and withdraw freely.
If you make it tradeable then you will have little control over the price. As I can recall about a year or year and a half ago someone who used Litecoin as ingame currency on his server was desperately looking for other solutions here, because of the instability of the LTC price crashed the whole ingame economy as LTC usage lead to inflated prices, disparities in production and some players were hoarding building plots and created an ingame property buble
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Well, I don't want control over the price. The game will always dictate what certain in-game items are worth. What people buy/sell the currency for outside of the game is entirely up to them.
Unless I make the in-game prices relative to an exchange value. Once it hits an exchange, make payouts/in-game purchase x BTC worth of my currency. Instead of saying, 100 game coins, the price is 0.001 BTC worth of game coins. So the rate will be fluid and not at victim to market fluctuations.