The race to be THE mobile social network is on. MySpace, the once-top social network now-fallen behind competitor Facebook, knows that having a strong stake in mobile is key to future ad earnings. Yesterday, MySpace announced agreements with Palm and Nokia, and claims that it will become the first social network to support every smartphone.

“Social networks are a telecos new best friend,” reads a Reuters headline. MySpace now counts 20 million unique users accessing the site from their handsets, 400 percent growth from last year, while Facebook has 15 million mobile users as of November, or triple the number from the start of 2008. And the figure is set to grow.  According to Jupiter Research, by 2012, some 600 million people will be accessing social nets through their mobiles.

Yesterday, DeWolfe gave the morning keynote at the Mobile World Congress in Barcelona, telling attendees that mobile is at the heart of MySpace’s plans to be a ubiquitous social portal. For many, the relaunch of the MySpace mobile site early next week is the major news.

The Associated Press reports that MySpace expects 50% of its traffic to come from cell phones in a few years, compared to just 15% today. Earlier this week, MySpace Mobile unveiled a revamped mobile site.CEO Chris DeWolfe said Thursday that the social network is looking into more mobile initatives like portable playlists, location-based apps and mobile commerce.

There are also many mobile-only social networks that believe theres room for new social networking kings on the platform, reports The Washington Post. Mocospace, itsmy, BuzzCity, GyPSii, and perperonity.com, to name a few, all believe they’ve created sites that exploit what’s unique about the mobile experience.