When Google released its very nice Nexus One phone many wondered what the search outfit was doing.

After all, it was about as familiar with the phone industry as a wildebeest knows about the DNA of pondlife in the Horsehead nebula. However it turns out that Google believes it is defending its online advertising empire. The outfit has been whispering to analysts telling them that the Nexus One represented the next frontier in the company's $20bn core business of selling advertising through search.

The logic is that Google has worked out that punters are accessing the web via their mobile phones rather than through their desktop or personal computers. Unlike Vole, which has largely missed the Mobile boom, Google wants a piece of the action, particularly as Apple is starting to lose its cool image in the market. and Singapore in the spring through Vodafone.

The cunning plan became obvious when Google spent $750 million to buy AdMob. Apple had to counter with a deal to buy rival mobile advertising service Quattro Wireless, but it was clear that Google had the head start.