Sony has apparently, with little to no advance warning, rolled out a microtransaction system for Everquest and EQ2. Clockwork Gamer has a writeup of the items and prices in EQ2.
Most of the items are cosmetic, such as cosmetic armor (EQ2 has cosmetic slots so you can hide the "hobo" appearence of the gear you're actually wearing), a minipet, and house items. The items go for a few dollars to as much as $10 for a full set of armor - the latter seems like a lot, but you don't outlevel cosmetic gear, so it's actually a permanent change of appearence for your character if desired. (Then again, you will be broadcasting to the world that you spend real money on your character, your social consequences may vary.)
The exception, which could have serious ramifications for subscription MMORPG's going forward, is EXP potions.
Selling exp for cash
EQ2 has a total of three separate forms of exp (adventuring - what other games would think of as normal exp - along with tradeskilling and alternate advancement). The new store allows you to purchase potions that boost the exp flavor of your choice. The potions are available in several flavors, including $1 for 4 hours of 10% bonus, $3 for 4 hours of 25% bonus, or $10 for 2 hours of 50% bonus.
EQ2 is not without other forms of bonus experience. The game has an equivalent of rested state exp, another bonus to your alts if you have a character at the level cap, and "veteran" awards that refill your rested state. Anecdotally, it sounds like recent changes have also drastically shortened the time it takes to level, so existing players have been leveling faster than ever in any case.
Technically speaking, the game isn't selling exp outright - you do still need to play the game to receive the extra exp. The fact is, though, that players who pay will advance faster than players who do not. Commenters on MMO Quests, where I first saw this story, are questioning the fairness of this bonus exp, especially in the context of the game's PVP servers. The move could also create pressure on players to pay for advancement or be left behind by their guilds.
Microtransactions and Double Dipping
The traditional concern about non-cosmetic microtransactions is that of "double dipping". In a subscription-based MMORPG, you're already paying to play the game. Lazy/greedy designers might be tempted to balance the game around the microtransaction items in order to boost revenue.
For example, the MMO Quests commenters were most concerned about the rate of alternate advancement experience. Sony now has a financial incentive not to make AA experience easier to obtain - doing so will literally hurt their sales. Instead, they could just say that players who are dissatisfied with the rate at which they gain AA's should pay an extra $5 per hour. How far that approach can go before players decide to abandon BOTH the microtransactions AND their game subscriptions is anyone's guess.
If nothing else, it's not encouraging that Sony literally rolled the system out onto their live servers before posting the information on what the service does. The perception is likely to be that they knew the changes would be unpopular, were not interested in the feedback, and decided to press on anyway. That could very easily backfire.
This move is obviously going to be watched very closely by the folks at Blizzard, Tubine, Mythic, et al. This may be good for Sony's bottom line (or may cost them subscriptions), but it's also opening a can of worms that most devs have been hesitant to open. Every single decision with any bearing on exp will, from this day forward, be colored by the reality that experience is now available for money. Making exp easier to earn in the future will literally devalue achievements previously purchased for cash. (In fact, Sony was deliberate to alter their TOS to make it extra clear that they believe they're allowed to do this.) Any achievement that is perceived as too difficult, such as, say, the exp curves for the next expansion, will be seen as an attempt to drive sales of exp potions.
My personal opinion is that the exp curve should be set at a level that makes playing the game enjoyable. If the game is well-served with a 50% increase to exp, then the devs should increase exp by 50% rather than charging $5 per hour for the best rate and leaving everyone else to progress at a slower, less fun, speed.
However, as I've explored here in the past, there is a strong demand to skip past old content in WoW - nearly half of my readers said that they would be willing to pay fo start a new character at level 55. Meanwhile, MMORPG's cost money to develop, and the studios that aren't Blizzard have to make money somehow. I suspect that most players would rather see an ill-thought-out microtransaction store than see their game closed down. Perhaps both groups can go home happy with relatively few ill-effects on the rest of the market.
To sum up, well, this post is a lot of words that add up to "I don't know what's going to happen". I doubt that anyone does. This might not even have major ramifications on any game outside of SOE - to my knowledge, no one has directly copied their Exchange Servers (with an official EBay-like "sell your characters/stuff for cash" interface) yet. Microtransactions are, in all liklihood, here to stay. I just hope, for all of our sakes, that they can be done without ruining the quality of the games for people who don't pony up.