With more than 750m users, Facebook is the world’s largest social network. So it’s no surprise that marketers have flocked to the Facebook in an effort to reach consumers online.

But Facebook’s COO, Sheryl Sandberg, knows that multinational brands and Madison Avenue ad agencies aren’t necessarily the most lucrative group of ‘marketers‘ her company can court.

Sandberg, of course, hails from Google, and it’s certainly not lost on her that Google’s cash cow, AdWords, has succeeded by democratizing online advertising.

Yes, major brands and agencies spend big bucks on AdWords campaigns, but there are millions of small businesses using the self-serve advertising offering as well. It’s those small businesses Sandberg is thinking about most today as Facebook gears up for an IPO in 2012.

Sandberg told USA Today ”My dream is really simple. I think every small business should…be using Facebook. We’re not going to stop until all of them are using it to grow their business“.

With that in mind, the Facebook COO is taking a page from Google’s playbook and is readying a plan to offer $50 in free advertising credits to as many as 200,000 small businesses.

Will it work?

Based on her experience at Google, Sandberg is confident. “For $50, most small businesses can target every single person they need to target at least once, and then they can grow their business from there“. In theory, it really is that simple, but Sandberg’s confidence may be misplaced.

Despite the fact that many small businesses use Google, there’s also no doubt that many small businesses that have tried Google have struggled.

From difficulties setting up a campaign to challenges creating effective campaigns that deliver ROI, anyone who has worked with PPC for any length of time knows that very few people succeed without some level of education and effort.

Understanding this, it’s not too difficult to explain why Google is placing more emphasis on making phone support available to its advertisers.

Facebook will face similar challenges in educating and supporting small business advertisers, but it’s no Google either. Arguably, Facebook’s challenges are likely to be even more pronounced.

After all, the efficacy of Facebook ads has been questioned repeatedly, and continues to be questioned, ads featuring pictures of beer notwithstanding. And there’s a good reason why. Facebook lacks what Google delivers in droves: intent.

From this perspective, Facebook and its COO shouldn’t be concerned with whether they can lure small business owners to Facebook with $50 in free ad credits. They almost certainly can.

They should, however, be concerned about their ability to keep them around once that $50 in free credits has been used. If the fact that Google is still trying to win over small business owners is any indication, Facebook will have to do a lot more than to earn the ‘like‘, if not love, of them itself.