There IS a potential for overlap between MMORPGs and gambling. The best example of this is the scam - sorry, I mean game - Project Entropia. Its a MMORPG that's been around for a few years now. It doesn't have a monthly fee - the game is 'free' to play. However, there's basically nothing to do in the game without spending money. To do anything in the game beyond walking around, you 'purchase' PEDs (Project Entropia Dollars) at a specified currency enchange rate (I believe its 1USD = 10PED.) You can purchase as many PEDs as you want/need. More than that, you can reverse the exchange, and turn in PEDs to get real-world money back (there's a 'service fee' associated with this, of course.)
That in and of itself doesn't QUITE rise to the level of gambling. The bigger issue is the way the game's economy works. Specifically, to kill monsters, you need to buy ammo. The monsters, though, rarely drop as much money as it costs in ammo to kill them. You'll spend 3PED worth of ammo to take something down, and it'll drop 2.5PED. Every once in a while, you, you hit the jackpot - monsters may drop 10PED, 50PED, 100PED, or even much more. Very rarely. You only have to play the game about 15 minutes before you realize that its basically a slot machine with a really fancy interface (but it is kind of fun
) No matter what you do, you guaranteed to lose in the long term.
More 'traditional' MMORPGs, though, I really don't see any real connection with to gambling. I mean, sure they maybe have a card game or something, but eh. A few specific differences between normal MMORPGs and casinos that I would list:
1) Connection between the money paid to play, and the game experience: in 'regular' MMORP, the game experience is not affected by the money paid to play the game (beyond having to pay to gain access for a specific period of time.)
2) In an MMORPG, gain over time is expected. You should, in the end, always have more than what you started with (whether its gold, experience, or items.) A gambling-type game is based on continuously losing (PE tries to fake this with a skill system. The secret there is that the skill system virtually doesn't do anything, not to any measurable degree. As you get really high skills, MAYBE the house advantage shrinks a percentage point or two, so you don't lose money quite as fast. You're still guaranteed to lose money, though.)
3) 'Cash-out' - there's no way to 'cash out' of a MMORPG. Selling stuck on eBay to suckers isn't in the same category as the game-maker actually mailing you a check. The difference has a lot to do with point 2: if the MMORPG maker isn't involved, then they don't care who makes the gold because the amount of gold in the economy doesn't affect them. With a cash-out option, though, you have a game that has to guarantee that you 'lose'.
There are probably more, but those are the most important ones, I think.
