Brian Storey, creative partner at direct agency Wand, says players accept ads in games "because it makes them more like real life". He adds: "If a brand harnesses this in the right way, it can reach its audience at home in a relaxed atmosphere, creating loyalty."
Who's doing it?
Obama placed an ad in Xbox 360 game Burnout Paradise. It featured the presidential candidate in a billboard message that encouraged players to register to vote.
Justin Townsend, chief executive of the company that created the ad, IGA, says: "This was an extremely savvy move by the Obama campaign. It addressed 18- to 34-year-olds and speaks volumes of the growing importance and influence of in-game advertising."
Reebok ads are soon to appear in the free-to-download online game Football Superstars. Elsewhere, Nokia and Virgin Media have a strong presence in virtual world Second Life, where the former has created a gallery that lets players share photographs.
The lowdown
The in-game ad sector was reported to be worth £150m globally last year. This figure has been predicted to more than double by 2010.
Research from Nielsen Games shows that 80 per cent of consumers find playing computer games 'just as enjoyable' when ads are featured.
Paul Hicks, head of brand experience at Attention, says: "The channel is expanding because it is extremely targeted. Online gaming requires players to register - you can mine data at this point. The target audience is also clear from the profile of players buying the game."
Google has entered the space with AdSense for Games, which will allow video, images or text to be displayed within online games. The amount of time an ad is shown on screen is measured. Online ads can be targeted to a specific region and a game's target audience will define to whom the ad is targeted.
"In-game ads offer the ability to run tactical campaigns with little turnaround time," says Townsend.