Google's Grip Tightens

"DoubleClick is emphatically the No. 1 player in the display ad market and has incredible market power," says Joe Apprendi, CEO of online ad network Collective Media. "In fact, that's why Google is so excited about this particular acquisition."

Of course, investors expect growth from Google as well. The company's shares closed Wednesday at $710.84, up 54% on the year, giving the stock a price-to-earnings ratio (P/E) of 34. The company also has a P/E-to-growth ratio of 1.3, meaning that analysts expect it to grow earnings about 35% a year for the next five years.

Bringing DoubleClick into its fold will be critical for Google's effort to meet those steep expectations.

Selling display and search ads together will give Google a powerful sum greater than each of its parts. Each form of online advertising is more effective when used in tandem -- and advertisers want to see the impact that spending on one type of format is having on the other.

According to a 2006 study by aQuantive (now owned by Microsoft), users who saw both display and search ads from the same advertiser were 22% more likely to click on an ad than users who saw only one form of advertising.

Flashy banner ads can help spark interest in a company or product, convey an advertiser's message, or catch a user's eye in a way that text ads can't.