We all know b2b and b2c, and even b2b2c. I'd propose that an emerging software business model is b2e2b (business to employee to business). While it hasn't been called out clearly like this (trust me, I've 'Googled' it) there are many companies that are already using this approach (Yammer, Dropbox, Xobni and others). The way it works is that a company builds a product that can be accessed directly by a single employee of an organization. As the number of users within a company grows and reaches a critical mass, the company then has a salesperson contact the organization to make the upsell -- e.g. business to employee to business.
Of course, this model is interesting in its own right. But there are much larger implications for enterprise software. Chris Dixon and others have talked a lot about the fact that enterprise technology is far behind consumer technology. As I've written before, I believe that the reason for this is that enterprise technology can get away with being bad. For example, if you're a payroll provider and you provide a lousy interface for employees you can get away with it because you only have to sell one person in HR on your product (and then they force ten thousand people to use it). But if you're a consumer site like Mint.com you can't get away with being lousy because you have to sell 10,000 people, one by one. You have to be great or you'll fail.
And this is why the b2e2b approach is so important. It’s radically changing the way enterprise software is built and sold. And as a result, we should see the quality of enterprise technology begin to catch up with consumer technology. And when it does, those big b2b companies that continue to rely on their brand or their sales force to drive sales will begin to collapse.