Agency explores further global opportunities.
Mobile has come of age but numerous marketing challenges remain.
Firstborn employs 65 and counts Pepsi, AT&T, and Wrigley among clients.
Companies partner to bring mobile advertising network to Japanese market.
Japanese holding company is said to have offered $600M for the digital agency, according to reports.

June 6, 2012
1:00pm ET / 10:00am PT