RMT is one of the largest game changers to the video game market in recent years. It is known as many things, micro - transactions, item malls etc. However they all come under the banner RMT. There are 2 main types of RMT associated with Video Games. Legitimate, developer implemented systems, and illegal, "cash for gold" stores.
Illegal RMT transactions
Most common to the MMORPG market is the "Chinese Gold Farmer" syndrome. This is where players will go to outside websites, pay real cash for fake, in game cash in return. This has been a very popular, million dollar franchise. The most famous example of this is the World of Warcraft Gold farming. Developers are trying as hard as possible to oust this illegal transaction of money for gold. Look into Eve Online's PLEX system for a great example of developers combating illegal RMT.
Legitimate RMT / Item Stores etc
The item store business model has seen a massive boom in recent years. Also known as "Free 2 Play," these games imply that you do not need to spend any money to enjoy said game. However within a item store, you can purchase items to improve your character, gain exp faster etc etc. Some games do this better than others. A major issue with the item store model is balancing people who pay for items, versus people who do not. Developers do not want to scare potential customers away because they keep getting "owned" by players who "pay to win."
Most f2p MMORPG games uses an internal medium for their item stores. Rather than saying, X item is worth 15 dollars, they will use a fake currency, separate to the ingame currency that players can transfer real money into. A simple example of this executed well is the G1 Coin system used in ALL GamersFirst games. In this example, players exchange Real Money for G1 Coins, which can then be used to purchase items within all of their games.
Non F2P RMT
Recently there has been an influx in games using RMT's to enhance their games, even if they are not free to play or Massively Multiplayer. A great example of a successful RMT within a game is Team Fortress 2 and Portal 2. Both of the games are baught with money, but you still have the option to spend real money on items within the game. (TF2 has now gone F2P, but at one point it was a game you had to first buy). Now the ever popular Monday Night Combat is entering the PC F2P market with RMT in its latest "Super" Edition.
A great example of RMT in a "pay 2 play" game is Eve Online. Recently they have added a store that sells clothing for player avatars, which players can buy with real world money. The most popular MMO of all time, World of Warcraft, even has RMT within it, where players can pay for mounts, pets and other services.
Many MMO's charge a real money fee for services in their games. This could be moving a character to a new server. Re-naming your character etc. In some games, namely WoW, you can pay to change your characters faction, even its class.
Please note Team Fortress 2 is now a fully F2P game.
F2P Non-MMORPG RMT
More and more genres are taking the RMT business model and using it to make far more money than they ever would as a boxed game. The finest example of this is League of Legends. This is a DOTA style game that is free to download and play. However real money can be spent to unlock new characters to play with, or different skins for the characters. LoL has become one of the most popular F2P games on the internet, and is becoming an E-Sport with immense worldwide popularity.
RMT is here to stay
There is no doubt, that RMT is a hugely successful business model when implemented correctly. F2P MMORPG's are growing by the day, games there where once pay to play are transitioning into F2P, item mall games. Great examples of this are Dungeons and Dragons Online, Lord of the Rings Online, Fallen Earth, Aion, and many others.
In short, the prospect of spending less than the standard subscription fee has revitalized games in the MMO market. This is why we see it transitioning more and more into other genres, including FPS's and RTS's.
Full price retail games with RMT
The latest RMT system is coming built in to full price video games. 2 of the most high profile games with RMT built in both come from EA, Dead Space 3 and Mass Effect 3. These games have options to purchase item chests or extra crafting items with real money. Both games offer the ability to get the same things through simply playing, but at extended time input. Another example of RMT in full price games is coming in sports games. Fifa Ultimate Team offers players the chance to spend real money on virtual card packs, for unlocking new players and items. the Ultimate Team is such a money maker for EA that they have said it will not be going anywhere anytime soon.
So far RMT in full price games has teetered on the edge of being completely wrong for the end user, but so far companies have managed to walk the line carefully. How long until a full price game jumps in the deep end, with an unlock everything for 20 bucks?