Microblogging is the quintessential "keep it simple" service.  So when a vendor adds a seemingly minor new feature, that's relatively big news. (Remember when Twitter added "retweets" last year?) Naturally, when Yammer announced its "community" functionality last week, it was immediately followed by a few gushy reports on what a game-changer this was. Rather than go by the demos, I waited until the service actually became available yesterday to have a look.

Yammer describes itself as "the leader in Enterprise Microblogging and Real-time Communications," but it's basically Twitter for the enterprise. With Yammer, though, a "network" is automatically created when [email protected] joins, and messages are only shared within your domain. They're not public.

The big change for Yammer is you can now create "communities," which can be joined by users from different e-mail domains. This means you can now use Yammer to work with external parties, too (invite people @anothercom.org).

Right now, however, I'm not overly enthusiastic about it. The functionality is problematic on two extremes: the casual user and the power user. For the casual user, it's a bit confusing why the "community" you've created shows up as a "network" (what's the difference?). It's still not really difficult to use, just not very intuitive, especially once you start switching between "networks."

And for power users, the constant stream of consciousness across multiple networks can become a bit much to manage; there are no sophisticated tools for filtering and organizing Yammer messages yet. (If you're an avid Twitter user, imagine keeping up with multiple accounts and hundreds of users -- through Twitter's web interface, without using a client application like TweetDeck or CoTweet.)

So until the usability and/or tools get a bit better, I think the sweetspot for Yammer continues to be small, tech-savvy companies. Glowing testimonials from Deloitte and Alcatel-Lucent notwithstanding, the figures seem to back this up: there are currently some 60,000 networks -- but with an average of 10 users each. Yammer has the potential to do a better job in the enterprise than most of the bolted-on microblogging that you can find now in nearly every product in our Collaboration & Community Software research.

But Yammer isn't quite there yet.