This “what is a blog” thing is quite an area of contention, I’ve noticed.
To one local contingent on campus, a blog is an online journal. This single poster throws their innermost thoughts into the mist, occasionally getting comments from outsiders, but not necessessarily.
To people like me, ‘blog’ means something much broader. Blogs can be single-poster or multi-poster. They can have commenting features or not. They can form communities of interest and argument within themselves, or social communities, or not. They can be created by a single inquirer drilling down on one topic of interest (like andrew sullivan’s about politics). They can have no text entries at all and be collections of pictures or audio files. They can be events unto themselves (mobblogging).
The one hallmark of the blog is the time-dated entry, indicating that it’s not just another website put up in haste and abandoned. Blogs tend to be more actively changed then traditional websites, and those changes are immediately noticable. That energy seperates blogs from other websites.
Another hallmark is the archives sections that divide the content by time period or category or both. Over time, this aggregation of content builds up and means something that a collection of emails or a distributed list doesn’t.
Blogs are useful for basic knowledge management because they create a gathering place and a searchable repository for information, displayed chronologically and by topic. Email gets lost, people drop out, and things change, but blogging a project group’s interactions assures that the expertise and process that the group develops and innovates as they progress doesn’t get lost in the chaos of employee turnover or forgetfulness.