Google (NASDAQ: GOOG) CEO Eric Schmidt often says that the mobile frontier is the next biggest opportunity for Google. In terms of the math, he's correct: there are many more cellphones in use worldwide than PCs -- all it takes is to get customers accessing the web on their phones. So far, success has been mixed, however, Apple (NASDAQ: AAPL)'s iPhone is changing the game. iPhone users are going on the web constantly.

The web search giant has just taken a large leap in that direction, now that it has announced YouTube Mobile availability on millions of existing cellphones. The more customers that buy advanced, 3G-capable wireless phones, the more potential customers Google will have accessing YouTube content and even uploading videos directly from their handsets.

YouTube mobile product manager Dwipal Desia indicated, "It's basically the full YouTube experience you can get on the desktop -- on the phone." With YouTube easily the world's most popular online video property, can Google transfer this to the mobile arena in the next year or two? Getting customers to use YouTube Mobile is the largest barrier -- because once you've used it, it's hard to resist (from my experience, anyway).

Although Google referenced the iPhone and phones from service provider Helio, the company did say that the full YouTube video experience was not available on handsets from the second-largest wireless carrier, Verizon Wireless. The next step, of course, will be for Google to find out how it can monetize YouTube Mobile.