What do Twitter and Facebook have in common? No, it isn’t how Facebook has been trying to copy Twitter. The answer might surprise you.

To date there are two prevailing business models on the web: paid subscriptions and advertising. The former has all but been a flop, except for in the adult entertainment industry. The latter has been having trouble lately with a waning economy and more demanding advertisers. And try as they may, the industry seems hard pressed to come up with another way to turn a buck on the web. Sort of.

There is actually a third, not as well known avenue to making a buck on the web that some companies have been profitting from for a long time. That is, products and services aimed at the corporate client. After all, where regular Internet users are on the continual hunt for free services, companies live in the reality of having to pay for the services they use. An example of this mindset was Jason Calacanis’s plea for a professional Twitter account. Two years later, and after much speculation as to how they’d make it profitable, Biz Stone started talking about pro accounts.

So how does Facebook fit into this scenario? After all, their primary user is the regular, not-too-tech-savvy person. But, the very same people who spend half their day on Facebook also work for companies. These people, like in any company, need to communicate with their coworkers on projects and shared tasks. I’m willing to bet however, that those people don’t spend nearly as much time on their company intranet as they do on Facebook. So why not bring the tools of business to the network everyone is already using? Why not create a professional services division of Facebook? A secure, private company Intranet for rent built on everyone’s favourite social networking platform.

Besides, some companies have already started using Facebook as their intranet anyway! So Facebook, what are you waiting for?★