The console makers are on to a winner with these so called "micro transactions", providing relatively cheap add on content for games via digital download. Microsoft's Xbox Live Marketplace is the first example we've seen get released into the wild, with people buying credit (and that's a critical part of the equation) for people to spend on items ranging from wallpapers to customise their console to add on maps and items for games.

Some of the stuff, like the Oblivion horse armour for example, has received a mixed reception from gamers. However they have been spending their credit, and Call of Duty publisher Activison has reported that they have sold almost $1 million in expansion maps for CoD 2, the most played multiplayer game on Xbox Live.

That's a serious amount of ongoing revenue intake, but the really surprising thing is that people have also been spending their credits to purchase things that, in the past, PR and marketing types would pay you to take. Things like wallpapers, to "customise" your desktop, can only be provided through the Xbox Live Marketplace, and so it is a sellers market. People have been literally buying promotional materials - only, when you spend "1000 credits" as opposed to "$12.50" it makes the medicine go down that bit easier.

Of course, a stingy person might point out that in games like Day of Defeat: Source and Red Orchestra we're getting bonus materials just as good as the Call of Duty map packs for free. Indeed, there was a time (once upon a better time...) when we got map packs for free. EA have tried selling smaller expansions for PC games, like the Battlefield 2 booster packs, and the exercise has largely been a failure. It seems that this sort of success story for publishers will only work in the highly managed, "sellers market", of something like the Xbox Live Marketplace or Sony's upcoming answer on the PlayStation 3.