So, with the launching of Facebook at Work, Facebook wants to become your professional networking platform of choice, does it? Well, speaking as a sample of one, I don’t think so. And it all comes down to one key reason that I’ve talked about in the past, but for some reason, Facebook doesn’t seem to get – social modality.

Social modality is not a tough concept to understand. I’m one person in my office, another on the couch. The things that interest me in the office have little overlap with the things that interest me when I’m “sofa-tose” (nodding into a state of minimal consciousness on overstuffed furniture). But it’s not just about interests. It’s about context. I think differently. I act differently. I react differently. And I want to keep those two states as separate as possible.

Facebook seems to understand the need for separation. They’re building out Facebook at Work as a separate entity. But it’s still Facebook, and when I’ve got my business persona on, I don’t even think of Facebook. Neither, apparently, does anyone else. In 2010, BranchOut tried to build a professional network layer on top of Facebook. Last summer, it changed its business model. The reason? A lack of users. When you think of work, you just don’t think of Facebook. If fact, there’s almost an instinctual revulsion to the idea. Mixing Facebook and work is a cultural taboo.

When we look at the technologies we use to mediate our social activities, different rules apply. It’s not just about features or functionality – it’s about what instinctively feels right. Facebook is trying to create a monolithic platform for social connecting and that doesn’t seem to be where we’re heading. Rather than consolidating our social activity, it’s splintering over different tools and platforms. One reason is functionality. The other is that socially; we’re much too complex to fit into any one particular technological mold. I wrote a few months ago about the maturity continuum of social media. The final stage was to become a platform, which is exactly what Facebook is trying to do. But perhaps becoming a social media platform – at least in the sense that Facebook is attempting – isn’t possible. It could be that our social media personalities are too fractured to fit comfortably in any single destination.

Facebook’s revenue model depends on advertising, which depends on eyeballs. It’s a real estate play. Maybe to be successful, social has to be less about location and more about functionality. In other words, to become a social media platform, you have to be a utility, not a destination. Facebook seems to be trying to do both. According to an article in the Financial Times (registration required) Facebook at work will offer functionality through chat, contact management and document collaboration, but it will do so on a site that “looks very much like Facebook,” including, one assumes, ads served from Facebook. By trying to attract eyeballs to drive revenue, Facebook won’t be able to avoid mixing modality, and therein lays the problem. I suspect Facebook at Work will join an ever-increasing string of Facebook failures.

LinkedIn isn’t perfect, but it has definitely established itself as the B-to-B platform of choice. It fits our sensibilities of what a professional social networking tool should be. And it doesn’t suffer from Facebook’s overly ambitious hubris. It hasn’t launched “LinkedIn at Home” – trying to become the social network platform for our non-work life. It knows what it is. We know what it is. Our social modality isn’t conflicted. Facebook is another matter. It wants to be all things social to all people. I suppose from a revenue point you can’t blame them, but there’s a reason I don’t invite my co-workers to my family reunion – or vice versa.

Someday Facebook will learn that lesson. I suspect it will probably be the hard way.