Mochi Media is helping to define the future of casual gaming on the Web — not through new games, but by showing how games can be monetized and distributed across the Web.

The company says it’s seeing 30 percent growth a month, and this week it added on massively multiplayer online (MMO) game portal Aeria as a partner.

What Mochi Media offers is two closely connected tools used by game developers. MochiAds is Mochi’s advertising platform, launched last October, which inserts ads directly into games. The second, MochiBot, is an analytics tracker that reports back with statistics as a game is picked up by different portals and Web pages.

Mochi’s ad platform allows everyone to benefit from a game being shared. Aeria Games, for example, gets to take any games it likes from Mochi’s community of over 2,000 independent developers. Those developers, in turn, get revenue back from the advertising that’s embedded in the game, and benefit from more traffic to their site.

Although Aeria has a formal agreement with Mochi, no agreement is really necessary — any gaming portal or site can “steal” the games for themselves, and the advertising guarantees that the developer will still be paid, while a link to more games at the end sends players their way. The closest comparison is an embedded YouTube video, which shows links to other videos when it’s finished playing.

The MochiBot tracker helps small developers see just how widely their games can spread. Bloons, one of the most popular casual games at the moment, has spread to 1,400 host sites and over 30,000 individual pages, according to co-creator Chris Harris, but he wouldn’t have been able to see just how many sites had it without MochiBot.

MochiAds isn’t the sole source of income for a game like Bloons; separate advertising can also run on the developer’s home site. Because MochiAds is driving players back to their site, there’s often a double benefit between the in-game advertising and a boost in visitors far beyond what developers might see if they tried to keep their games exclusive to their own sites. “People that are new to this space don’t understand, it’s not just about revenue,” CEO Jameson Hsu told me in an interview.

The question is whether advertising alone will be enough to pay off developers for their creations. I’ve heard from several top developers that they make, at minimum, a living wage from their creations — but those are all individuals or small teams who have one of the few games that makes it big.

For the moment, there’s not enough revenue floating around to support large teams or companies, which means that various pay-to-play models will continue to be popular with some developers, while micro-transactions will work for others.

Ad revenue will go up over time. The total ad spend for games is estimated to roughly triple over by 2011, according to a 2007 eMarketer report. New forms of in-game ads like video, which Mochi will begin doing soon, may help drive up returns on individual ads, and the company also has a competitor called Neoedge, which will compete to offer better rates.

Mochi Media is based in San Francisco, and is funded by Accel Partners, which put an undisclosed amount into it in the second half of last year.