Just One Of Seven...

How do you get players to make that sort of time commitment? One way is to appeal to their vanity. On Pogo, only paid subscribers get customizable avatars and badges that advertise their achievements to the community. On Kongregate, players that complete specific challenges in games can earn virtual, collectible cards that will soon be usable in a Pokémon-style online battling game.

"One of the things that games do, besides being fun, is they do this trick that you feel like you're accomplishing something," Greer says. "If nobody else can ever see your accomplishment, it doesn't mean nearly as much. One of our investors said 'every successful consumer website has to appeal to one of the seven deadly sins.' For MySpace maybe it's lust, for a financial site it's greed, for a game site it's pride."

Even if you don't charge for your content, that pride can also work to your advantage if you've built a community of players that want to advertise their support of the game. Players that donate $5 via PayPal to free online games kdice and gpokr get a small star next to their online avatar. Some players have dozens of stars next to their names, telling the world that they've given hundreds of dollars for a game they could have played for free.

"I doubt [the stars] are a reason exclusively for anyone to donate, but it's definitely an added bonus," said Ryan Dewsbury, software consultant and developer of the games. More than vanity, though, what really convinces people to donate, Dewsbury says, is a sense that the money will go towards making the game better. "I love the sense of community that all the players bring to [kdice and gpokr]," he said. "We all feel somewhat motivated to see the games improve."

If that's not enough, Dewsbury says he's currently developing a change to the donation system that will give players even more reason to voluntarily hand over their cash. While he's coy on the details, Dewsbury says the change will help donators in the game without unbalancing the experience. "The change gives more value to people buying stars... I would call it meta-game value. People are more willing to support it if they get extra value back."

Though advertising still makes up 80 percent of his revenue from the games, Dewsbury seems less enthusiastic about the future of the ads on the site. "More ads doesn't necessarily translate to more money. I like simple interfaces, so I like ads to be clear and unobtrusive. It's also an image issue -- I think too many ads can push a developer away from a community."