Mobile ad network Greystripe Wednesday announced an expansion effort that includes the opening of four new sales offices in Atlanta, Seattle, Minneapolis and Phoenix.

Acquired last April by ValueClick, for $70 million the firm has brought on nine executives from various companies, including AOL, Millennial Media and Specific Media, in connection with the new sales offices. The new hires are

 ·        Brian Pearlman, senior account executive, from Millennial Media

·      Ryan Bleich, senior account executive, from AOL

·      Chris Backschies, regional sales manager, from WeatherBug

·      Terah Bocchi, senior account executive, from Belo Phoenix

·      Jeff Margolis, senior account executive, from Adfusion

·      Bill Kramer, regional sales manager, from quadrantONE

·      Josh Parker, account executive, from Specific Media

·      Matt Sexton, regional sales manager, from RadiumOne

·      Ken Yonan, regional sales manager, from Specific Media

Greystripe says it has doubled the size of its sales, engineering and operations staff since May, while expanding its presence in Europe through a series of partnerships. Its ad platform serves billions of rich media impressions to more than 40 million mobile users across 3,500 applications and mobile sites.