Facebook has yet to make any significant money from mobile. Some critics, including Ironfire Capital founder Eric Jackson, believe that the rise of mobility will kill Facebook--or soon make it as irrelevant as MySpace is today.

To be fair to Facebook, it's one of many Web companies facing the same fundamental problem with respect to mobile: How do you make money? Facebook is struggling to fill the enormous gap between mobile page views and revenue. (Mobile users are worth about a quarter of a desktop user according to Digiday.) Potentially adding to the company's challenges, Facebook's CTO Bret Taylor--who largely oversaw mobile efforts--announced Friday that he will depart later this summer to work on a still-to-be-determined start-up.

It's worth noting that some companies are much further along than Facebook. Pandora just announced great mobile ad revenue results. And publishers like Conde Nast, CBS, Liberty Interactive, WSJ, Bloomberg, and Gannett are doing much better than most of their competition.

Let's dig into what's plaguing the newly public Facebook--and what the company might be able to do about it.

Facebook's Achilles' Heel

In terms of monetizing mobile, Facebook trails Google by a wide margin. Right now Google makes about $2.5 billion from mobile ads, a number that could reach $5.8 billion relatively soon. Its Motorola acquisition along with the recent hiring of Dennis Woodside--the man who is supposed to "crack the mobile ad market"--shows the company is going for broke with  mobile.

Why does this matter? Consider that Facebook grew up on the social Web--just when mobility was taking off. Now that social Web is morphing into a mobile one. While I have no crystal ball, this much is certain: Fewer and fewer will people buy proper computers. Mobility will become the primary means of connecting, especially in developing nations. If Facebook can't properly monetize its mobile experience, it may well turn out to be the company's Achilles' heel.

Can an Acquisition Solve the Problem?

Facebook has clearly shown a willingness to buy what it can't build--or what already has an established user base. Instagram was a case in point. It's possible the company will do the same with a strategic mobile acquisition.

Rumored to be at the top of its list is Opera--a company that makes a Web browser for mobile devices and computers. Opera's products generate 30 billion impressions per month and reach 35% of global mobile users. Last year, the company delivered $240 million of mobile ad revenue to publishers and reflected 20% of U.S. market spend.

If it buys Opera, Facebook could theoretically give Google a run for its money for mobile ad dominance. Opera arguably operates under superior model. The company carefully selects the publishers for its ad network. What's more, Opera is transparent about where each ad runs. As a result, Opera can charge more for CPMs because the quality is higher--you pay more to get more. Conversely, Google relies on lower-paying search and long-tail traffic, for a not insignificant part of its revenue.

Buying what you can't (or don't want to) build, of course, is fraught with risks, especially when you're a public company and your stock has dropped so precipitously. Despite the company's vast internal technical resources, Facebook's best option might be to make an other purchase here. Wall Street may not wait for Facebook to figure out mobile on its own.