This is quoted from my internal blog at work... I know that there are much better experts out there to answer this question... I hope some of them can respond and help me convince people how little I know :-)

First, a confession - I don't understand blogging.

What? You ask. How can you not understand blogging? You have written blogs, read blogs, wrote a blogging tool, talked about it more than you should, and debated the future of blogging with DBox and other luminaries!

I guess I would say that I have just begun to understand what is going on. I know that Winer and Co. have been blogging for years. I understand that permalinks, RSS feeds, and time organized posts are common to all "real" blogs. I have begun to understand the notion of the community as a standards body. Looking at new features like pingback and trackback, along with Sam Ruby's <xhtml:body> features I am begining to understand what an open community is.

However, I have also really begun to understand that these technical blogs are only one corner of the blogsphere. The last number I heard was something like one million people are blogging. Companies are begining to see blogs as the new place for marketting. Corporations are investigating blogs as new way of communicating internally, and externally.

I don't understand blogging.

It is nothing new. FrontPage provides better editing support. SharePoint works way better for document management. Exchange captures conversational dialogs better. Instant Messenger gives much faster change notification.

Why is it catching on? Why should anyone care?

Lets dispense with a buzzword... Democratic journalism. I think people mean this to refer to the features of blogging that allow an individual to post, or publish, their thoughts to the world. The web did this long ago. However blogs have a built in type of reputation system. Because blogs are an ecosystem of links, once you find a blog you trust, you begin to trust the blogs that site links to. Hence, when I post something to my site, I get credibility if influential people link to me. The democratic system means that the more people that link to me (re: vote for me) I get more influence. There are a lot more smarter people than I that talk a lot about this on the blog...

Blogs have been compared to newsgroups. It is interesting. In newsgroups there is no "uber" member. Everyone is equal. At first that seems great - however it makes it hard for people to filter out the noise. In effect, a blog gives me control over the "major" content of my newsgroup. I can post anything I want on the front page... anyone can add comments, link to me, etc - but no one else gets to be on the front. In this way blogs appeal to the ego of the blog owner, but also gives people visiting a blog a built in filter.

The most fundamental building block of blogs is RSS. I don't know how revolutionary RSS is compared to HTML or TCP/IP, but RSS is the heart and soul of blogs. RSS provides a crude "alpha" XML web service. It will evolve and become even better. Today, RSS gives blogs a way to publish their content in a standard way. Sounds simple. Which is what makes it great. With RSS as a standard, you can now have aggregators that troll hundreds of blogs and extract relavant information. You can extend RSS (being XML and all) and add features like full message content, Doublin Core fields, etc.

One reason I believe that blogs are great for corporation internal communication is the question of distribution lists. Inside of Microsoft we live and die by email. However the constant spam of email to large distribution lists ends up drowning out the important information. For many types of communication (but not all) blogs provide a better way of communicating. There are many cases where you as the publisher of a piece of information don't know who would be interested. Blogs are a way to "publish and forget" - you fire the information out there, and interested people will find it. Once I add our internal blog server to the corporate search service, suddenly I could find people that worked on products that I wanted to communicate with. Amazing.

I don't understand blogging.

I have a huge concern. Now that everyone is thinking about blogging - including Microsoft - I am worried that the normal thing will happen. People will spend a few minutes, maybe even read a book, about blogging and then think they get it. They will then spend the next three months figuring out how they can make it better. My advice - first learn. Seek first to understand, then to be understood.