Rick Cortese knew he was in a dicey neighborhood, so he played by the rules and made sure he locked his doors before he went to sleep. But crooks still managed to loot his home, sucking valuable possessions right through the walls. The theft happened in the virtual world of "Ultima Online," one of the first popular online role-playing games, but it was a headache nonetheless and an example of the kind of cheating likely to thwart game publishers as they try to push more customers online.

Although online worlds such as "Ultima Online" and " EverQuest" account for only a small chunk of the game industry today, it's a profitable chunk, accounting for $210 million in revenue last year. Game publishers and analysts expect the segment to grow significantly in the next few years--to as much as $1.8 billion in 2005 by some estimates. That's because online games based on popular franchises such as "The Sims" and "Star Wars" will start cropping up to lure mainstream consumers into the arena. Game companies are looking to subscription fees from online players as a major source of recurring revenue in the near future, with leading games publisher Electronic Arts predicting that 400,000 subscribers will be paying about $15 a month for "The Sims Online" by the end of its current fiscal year.