Free Pizza

Moreover, Linden Labs is growing. The company now has 250 employees - up from 120 this time last year - and has just set up an office in Brighton to cater for the growing subscriber base outside the US, which now accounts for 55 per cent of the total. (Britain is home to the third largest number of users, after the US and Germany.)

Perhaps most significantly, large companies are changing the way they use Second Life - a sign, Mr Rosedale said, that the world is maturing. After an early phase of thinking it was a new medium, like television, in which it was important to establish a 'brand presence', they are now realising the other benefits of an online 3D environment, he says.

Market research teams in retail companies might, for instance, use Second Life to assess a focus group reacts to a new store interior. McKinsey, the management consulting firm, said recently that Second Life and other 3D worlds would be a vital to any company attempting to reach out to the 'video game generation'.

"We like the idea that it can be repurposed as a platform," he said.

Several large challenges remain, one of which is search. Google can't index Second Life in the way it can the internet, meaning that it is hard to find the billion-plus objects floating around the world.

Companies have also requested the ability to conduct their experiments in more secure environments, in an attempt to guard against a now famous incident two years ago in which saboteurs distrupted an 'in world' interview with one of Second Life's best-known residents by bombarding the stage with giant virtual penises.

Mr Rosedale said that Linden Labs' engineers were working on being able to give companies a secure Second Life server which would sit in their offices and enable them to use the world as a tool, free from interference from public areas.

He acknowledged that there were still problems with the usability of the site - but he put these down to the size of Linden Labs' ambition, which was to allow a user to run an incredibly sophisticated product within their web browser. They would improve with time, he said, particularly as broadband speeds continued to increase.

Moreover, there was a precedent for Second Life's development, he said: nothing less than the web itself, which in 1996 was dismissed by many as a fad.

Explore Tech & Web

• Personal Tech

• The Web

• Gadgets & Gaming