wrote a great piece summing up the many ways Facebook and Google's trajectories cross, particularly when it comes to advertising. And as he points out, both companies have their strengths.

"The infusion of public IPO money will embolden Facebook to take on Google directly in areas where it's clearly weaker -- primarily advertising, but also search and mobile. Google will defend its turf while simultaneously attacking Facebook in social (and hopefully in identity services)," he writes.

That last part -- identity services that let you sign into a Website or account using your Facebook credentials -- is definitely something Facebook has a good hold on, and as Needleman points out, it's something Google needs to get better at marketing.

But Google is kicking it with mobile. CEO Larry Page, in a said the company is "seeing a hugely positive revenue impact from mobile advertising, which grew to a run rate of over $2.5 billion by the third quarter of 2011 -- two and a half times more than at the same point in 2010."

Can Facebook figure out how to get some of that pie? It had better -- its users are now using the social network more from their mobile devices than from their desktops.