U2 have performed gigs there and Duran Duran own their own island. Linden Labs' Second Life (SL) and other such massively multiplayer online role-playing games (MMPORGs) are the latest frontier and it's not just pop musicians that are exploring their potential.
SL does pretty much what it says on the tin: players control their virtual alter egos - avatars - to live an alternative life. SL offers hundreds of activities, from the mundane to the strange: you can make friends, gamble, hit the nightclubs or visit vampire castles.
But the game, like other MMPORGs, also has its own economy. SL '"residents" can buy land and create objects - pretty much anything, from buildings to butterflies - that they can sell to other players for the game's currency, Linden Dollars. Importantly, residents have intellectual property rights to their creations, and can trade SL objects outside the game in real currencies.
In August this year, SL had a user base of around 750,000, with 314,000 active players. Thousands are joining every month. World of Warcraft, an older MMPORG, claims to have 6.5 million players. Numbers such as these make these games difficult for companies, marketers and brands to ignore.
But worlds such as SL are built by players for players and can be resistant to outside commercial influences, observers warn. Richard Huntington, the planning director at United London, says the brands that will be successful in SL are the ones that interact with the game seamlessly and find innovative and imaginative ways of talking to players. "The industry has to ensure it offers customers something they want," he says.
One company is doing just this. Last week (Campaign, 15 September), Adidas set up a store in SL, to support the launch of its extra-bouncy A3 Microride trainers. SL residents can buy them for their avatars.
And Reebok, which Adidas recently acquired, is launching an SL version of its customisation service: players will be able to design trainers for their avatars and also order real versions for themselves.
Adam Hemming, the strategic account director for Reebok, comments: "The customisation angle fits in with our 'I am what I am' strategy and is the perfect way for us to use this medium."
"Reebok is providing consumers with something that they actually want to experience, not just bombarding them with messages," Hemming asserts.
But should other brands be joining the queue for the bandwagon?
Perhaps, Nick Adams, the group account director at MindShare Interaction, says, because SL offers an opportunity to reach an audience that can be difficult to contact. "People playing these games are totally immersed, so they don't really interact with magazines, TV or other media," he says.
But is it set to be just another adland fad? It's hard to say, Huntington argues: "In advertising, we always overestimate the short-term impact of new technology, but underestimate the long-term impact. We get very enthusiastic early on, then forget about it until it really is making a difference, and then we're too late." In general, he urges caution. "If a business has any doubt about whether to go into this arena, then they shouldn't do it. The people that actually understand the medium can be counted on the fingers of one hand."
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GAMER - Sam Laurence, 15-year-old schoolboy
"At the moment, the game doesn't have that much to it and there isn't a great deal to do if you don't want to build a house or buy an island. I have played it with money and without and it doesn't make much difference.
"I do like the game and the idea though, but I wouldn't really be tempted to buy something from there at the moment, whether it's from a company or a personal sale.
"However, as the world grows and the products and services that companies offer become more interesting, I think it will start to become more interesting, although the product would have to be pretty special for me to buy it in real life as well as in the game."
STRATEGIST - Richard Huntington, planning director, United London
"Brands and media agencies assume that these virtual worlds exist for their benefit, but companies need to exercise extreme caution when thinking about moving into this arena because it isn't a natural home for them. There is a saying that applies here that goes: 'Brands rush in where angels fear to tread', because they are scared of being left behind.
"These virtual worlds are built by consumers and not set up for commercialism. Parasitic commercialism will be rejected by the host. Brands can add to the conversation but only if they have something interesting to say."
CREATIVE - Ben Priest, executive creative director, Rainey Kelly Campbell Roalfe/Y&R
"It is something we have thought about doing and put work into, but it needs the correct media mix and the right client to be a truly viable advertising option. It will really work well for companies such as Adidas and Nike that have identical product offerings and need to create standout.
"However, any business using it will have to be extremely cautious, because the normal rules of marketing do not apply. We no longer have the right to reach out of a TV and bash people on the head. We need to give them something they want. The whole thing could backfire if you are seen as being the first company to soil this virgin landscape."
DIGITAL SPECIALIST - Adam Hemming, strategic account director for Reebok, Isobar
"The point of Second Life is to build your own identity and create something unique, so advertising used in the game has to reflect this or it just won't work. You have to offer the player something they can use. This will help in keeping it from becoming a gimmick.
"Because of the way these realities are built, the brands that are successful will be the ones where their ideas are spread by word of mouth, and players need to be impressed for this to happen.
"We have research showing that when you flash a message at people in multiplayer online role-playing games, the reaction is generally neutral because the players are too immersed for it to sink in."