Google and Facebook Account for Half of the Advertising on the Internet

Online advertising has been growing steadily, each year since the web came about. Barring some minor hiccups, Google has been riding the wave and even getting ahead of it.

So much so that 44 percent of ad spending on the web happens on Google sites alone, according to data from Zenith Optimedia. That's last year's figure as well, Google is expected to account for an even larger percentage this year.

It has grown for the past five years, almost every year, grabbing even more market share. Meanwhile, all of the other big players have been getting weaker.

With one exception, Facebook has been growing in the past few years as well. It only grabbed 3.1 percent of the ad expenditure in 2010, but it is going to have a bigger share this year. And with its greater focus on revenue, the years to come are going to be increasingly bigger.