IMHO, blogging is a redundant communication medium inside a company or organization.  How's that for controversial?  News at 11...

Companies could have had a "blog experience" as far back as 1996 using the first version of Microsoft Exchange using a combination of Distribution Lists (DLs) and Public Folders (PFs). 

We use DLs heavily within Microsoft.  I've heard our operations and technology group (OTG) say we have 25,000 DLs which is basically one DL for every two employees.  DLs are fantastic because they allow the user to push email to those people who are interested in a particular subject/topic/technology/product/...  The reason they're so pervasive is because using a tool that OTG developed called AutoGroup that enables anyone in the company (perhaps only employees) to create a DL (or security group) add members, etc.  By and large, the DLs are completely automated which is why 25K DLs is almost acceptable.  Assuming you've named the DL well (e.g. Office 11 Discussion Group) and its of interest to more than just you you're sure to have people join or send email to it.  We used to allow DLs to be created for social interests (e.g. Cyclists at Microsoft) but those have been moved to PFs too reduce operating expenses.   I think it is one of the more empowering tools we have at Microsoft and definitely allows us to share knowledge.  In my opinion they're part of our secret sauce for out executing other technology companies.  I've talked to non-IT companies (IT is a cost center) about pervasive DLs and I always get replies like "our users will create non-business related sites" or "the operational overhead is way too much."  Its possible but I'd take that risk over people not communicating any day of the week.  Communication is why each of us get a little smarter with additional blog syndication (assuming we're syndicating the right blogs).  Its sort of my paraphrase of (Bob) Metcalfe's Law.

PFs are analogous to Newsgroups (and in fact can be an NNTP server or retrieve NNTP feeds).  They're great for conversations because of the Outlook's Sort by Conversation view that lets you see the conversation thread complete with indentations.  We have thousands (if not tens of thousands) of PFs. PFs can be added to a PF Favorites folder which enable you to quickly go to those PFs of interest and most importantly, at least in my case, read and post to them while you're offline. One limitation of PFs is that you have to go into them in order to see what was newly posted.  You also have to be "in" them in order to post your reply or start a new topic, thus the pull.  Once you've read a PF posted message Exchange "remembers" and the next time you go to the folder as you would expect (or hope for) the message remains "read." Most importantly, Exchange enables a public folder to have an email address which means they can be a member of a DL. 

I like combining DLs and PFs because you get the best of both worlds.  DLs make sure the email goes to a wide group users which can speed up getting a response (they're sort of in your face unless you use a rule to put them in a sub-folder) .  PFs enable someone who wants to join in on a topic after it has taken place or who is recently employed to find an answer without having to restart an FAQ by emailing a DL.  The biggest mistake a DL owner can make is not creating a DL archive PF when they create their DL.  The second challenge is making sure the search tool(s) that you're using make it easy to find the archived message. 

Feature flash: RPC over HTTPS enables a user to connect Outlook to their company's Exchange server(s) over port 443 which makes it almost as easy as posting to your blog server.

I'm sure Notes/Domino has a similar way of doing DLs/PFs and so may GroupWise.  I don't follow the other messaging vendors that closely anymore.  Given that Exchange, Domino/Notes and GroupWise make up the largest share of messaging servers its with nearly everyone's grasp to have the ability to create a blog-like world right within their own company.