The comparison is a good one, though, as what Yammer offers is, broadly speaking, the features and functionality of Twitter but in a more private way that's geared for groups of employees to exchange short and frequent answers to the simple question: What are you working on?

Anyone can set up a Yammer account (I've done that as the screenshot above indicates). To do so, you have to have what Yammer calls a valid company email. They have blocks in place to not accept sign-ups from webmail addresses such as Gmail, Yahoo, Hotmail, etc.

Once you've signed up, you can then invite colleagues, etc, on your company-domain email system to join your network.

This is just like Twitter except it's behind your own email firewall, so to speak.

And just like Twitter, you can do these things:

• Set up a profile
• Follow/unfollow co-workers
• Get answers to a question
• Share a news article, document or link
• Participate in a discussion
• Look up a co-worker's contact info
• Search for a topic
• See what's popular and who's influential

Yammer adds quite a bit more, though, than what you currently can do with Twitter itself, such as:

• See threaded conversations (similar to what Jaiku can do)
• Add tags to your messages (such as what Hashtags does)

The basic service I've described is free. There is a pay-for model that offers functions such as managing members, setting password and other policies, IP address range settings, and more.

These aspects alone are likely to make the IT department feel more comfortable with a service that runs on another company's servers. In  the cloud, in fact.

Yammer also provides a desktop application (cross-platform and built with Adobe AIR, quite elegant) as well as mobile apps for the iPhone and Blackberry.

I can see a big appeal for a collaborative communication tool like this within organizations. You have all the benefits of Twitter but just within your own domain, as it were.

Yammer launched yesterday at the TechCrunch 50 Conference in San Francisco.