Maybe Microsoft’s claim that Google is the “world’s largest advertising company” may not have been so far off the mark if current predictions come true. Last year, Facebook leaped past Yahoo! to become the top seller of online ads. This year, Facebook will likely know how Yahoo! felt when that happened because Google is currently on track to surpass Facebook and become the top seller of online ads.

eMarketer reports that Google’s display business is growing faster than expected and, at its current rate of growth, is set to overtake Facebook in 2013. The percent of money Facebook generated from selling display ads is somewhat predicted to level off next year while Google looks to make out like gangbusters.

While Facebook’s revenue may level off, the percent of revenue growth between the company and Google is expected to be the same, about 48%. However, next year is a different story as eMarketer expects Facebook’s growth to drop considerably while Google will maintain the same percent of growth.

The previos forecast for the upcoming years by eMarketer estimated that Facebook would remain the top seller of online ads. However,

This forecast incorporates a stream of newly available data, including reported figures from major players such as Facebook and Google.

The forecast also features a significant upward revision for Google’s display business compared to previous eMarketer projections—a result of stronger-than-expected performance from the company’s mobile display business, YouTube’s growing role as a venue for premium display inventory, and strong growth from the company’s DoubleClick ad network. The strength of Google’s existing relationships with search advertisers has also been a tremendous help for the company’s display business, according to eMarketer principal analyst David Hallerman.

While Google’s ad revenue has grown like a happy fungus in the damp, dark corners of a forest, they may have revise their recipe for success following recent developments with how they can collect information about consumers in order to manufacture and tailor ads for the public.