Kelliher's exit follows on the heels of Virgin Mobile CFO John Feehan's resignation last month to become CFO at LifeLock, a company specializing in identity-theft protection. Feehan will remain at Virgin Mobile through its third-quarter earnings report, and will leave in mid-November.

After going public a year ago at $15 a share, Virgin Mobile's stock price has since tumbled to about $3 due to falling profits, revenues and net customer losses. During its second-quarter conference call in August, the company predicted improvements in the second half of the year and growth in 2009.

As director of mobile media services at Virgin Mobile, Kelliher helped developed the company's Sugar Mama ad program, which enables users to earn free airtime by agreeing to view ads, responding to branded text messages and completing surveys .

Before joining Virgin Mobile in 2006, Kelliher was national director of sales for The Lodge, which provides original music for TV commercials. More recently, he has also gained prominence as a frequent speaker and panelist at mobile industry events.

Kelliher's new responsibilities will encompass Platform-A's Third Screen Media mobile advertising platform, which already serves banner ads on the Virgin Mobile service.

This news story is important. I recommend that everyone read it.