Static IGA
These are messages which are hard coded into the game and cannot be removed or altered. They can appear as billboards within the game, posters on the walls or even as obstacles to overcome (In Splinter Cell:Chaos theory a glowing AXE deodorant ad comes as an obstacle for the player to overcome). Especially useful in single player role playing games (in the league of Tomb raider or GTA etc.), these advertisements are assured of a prime position and sufficient time in front of the player.
Dynamic IGA
Online Presence
Permanent online games (like Ragnarok, Second life, World of Warcraft etc) can persistently have advertisements in various parts of the game. These games get a major chunk of their revenues from this kind of advertising, as people registering for the game is deliberately kept cheap so as to ensure maximum popularity. They have all the properties of Dynamic IGA but a lot more flexible as the concept of the game is such that advertisements can even be placed on personal choices (like google ads).
Good or Bad???
I as a person, owuld be horrified if I came to know that the kinds of games I play, the duration of me playing them etc is the kind of information which the game designers can have at their fingertips. Don't ask me why, there're some things which people like keeping close to themselves, as private!
But being a marketing enthusiast, I can appreciate the ingenuity of this new medium of advertising. No wonder, various games are looking out for sponsors to be placed in their games. World favorites like FIFA, GTA, NFS etc are selling their spots at a premium ensuring a prime spot to the companies in front of a large audience. Moreover, these companies get a chance to be seen by a huge chunk of gamers across the globe who are (increasingly) turning away from television.
All in all, In Game Advertising is here to stay, and you better get used to it!!!!