I've already written elsewhere about the inevitability of in-game spam. Here are some supporting links (I'll be adding more as I discover them):
"Mmospam-bots: "Bots" created for the specific purpose of harvesting user data (via 'who is online' or 'what characters to is active on a given server') to then send spam (using the same bot or another bot) via in game messages (aka "tells") and/or via the in game mail system to advertise products for sale for real world currency." (EQ2-Daily)
"There is nothing that will kill the immersion factor of a game faster than an advertisement selling something in real world dollars (this also applies to "code authorities" who advertise real world products or service in a game but that is for another post). The scary part is that this is just now becoming something that is feasible, both financially, and to a point technologically, to companies. The total MMORPG player base has increased exponentially in the last 8 years, with that comes a.) more people playing a certain game (that might have the potential to purchase in game currency using real world cash) and b.) As games get more popular, more people will try to figure out third party APIs to hack the games, thus making the availability of a programming interface to a game more susceptible to scrupulous people trying to write code to create mmospam-bots.
These bots would harvest player information using multiple methods (for EQ2 what comes to mind is just doing /who commands in a zone to see who is online to send tells too, or crawling eq2players.com for an x day period looking for people who have advanced their character and sending them in game mail) and distribute advertisements via communication channels in a game." (EQ2-Daily).
"At 10:33 EST this evening, in World of Warcraft, I received the following 'tell' (direct person-to-person message): 'Adifdkd whispers: Hi, pls visit www.itembay.ca The low Price: $8.99=100G, $16.99=200G $40.99=500G $75.99=1000G. First Come, First Serve.'" (Edward Castranova at Terra Nova).