Spending on online advertising declined 3.4 percent to $22.7 billion during 2009, according to a report out today from the Interactive Advertising Bureau and PricewaterhouseCoopers. And while many companies hoping to make money through online ads would see that as bad news, today's report also was filled with some positive nuggets which indicated that the industry might be headed for a rebound.

For one, the fourth quarter of last year saw a record amount of spending at $6.3 billion. Secondly, the 3.4 percent drop is rather small compared to the double digit declines which occurred during the dot-com meltdown of 2001 (ad spending off 12 percent) and 2002 (ad spending off 16 percent).

“As consumers spend more of their time immersed in digital media, marketers are increasingly reaching them there—building brands online and making digital the central force in their cross-media strategies,” said Randall Rothenberg, president and CEO of the IAB, in a release.

Nonetheless, despite what appears to be a positive trend toward more online ad spending, we've seen a number of startup companies in recent months shift their businesses to areas where they don't derive as much money from ad revenue. Recent examples include Zillow.com with their mortgage marketplace and rental listings, as well as TeachStreet which recently unveiled an online payment system. Meanwhile, just yesterday we reported on how Cheezburger Network founder Ben Huh said a growing percentage of the company's revenue will come from book publishing and merchandising of physical goods.

"I am wrong so many times, it is not even funny. We were wrong. I mean, I was wrong," said Huh when asked about online ad revenue. "The company now generates an ever growing percentage of our revenues from non advertising, and we believe that that trend will continue."

At the TechFlash event last month, Madrona Venture Group's Brian McAndrews said that is is "very challenging to have a business that's just based on advertising."

Part of the issue for smaller companies is that the heavyweights -- think Google -- control most of the market. In fact, the IAB report found that the ten top ad selling companies accounted for 71 percent of the revenues during the fourth quarter. That makes it harder for smaller companies to make inroads.

Here's the breakdown of online ad revenue by category during the fourth quarter. (The accompanying chart is for the full year).

Search: $2.9 billion or 47 percent.

Display: $2.3 billion or 37 percent.

Classifieds: $594 million or 9 percent.

Lead generation: $374 million or 6 percent.

Email: $77 million or 1 percent.