The US Federal Trade Commission is asking for declarations following complaints that Google's purchase of mobile advertising company AdMob would stifle competition.

Google has upped its offer for the acquisition of video compression specialist On2 Technologies by $0.15 a share, and will offer 0.001 of a share of its own in exchange.

Google has gone on a spending spree in the last few days, buying mobile advertising specialist AdMob along with voice-over-IP company Gizmo5.