Whence the blog?

As someone with professional and personal interests in both print and digital media, I am always curious about how new media and genres build upon earlier forms and technologies. To help me think about historical analogues to the blog, I've been asking my colleagues about earlier genres that share characteristics with the blog. First, though, I had to list characteristics of the blog that could be considered separately from its connection to the Web, at least for the purposes of analysis. Here's what I came up with (allowing for the fact that any description of a genre amounts to a stereotype that won't do full justice to the complexity of any form of human expression):

• First person persona. Simply put, blogs typically have single authors identified by name, or groups of authors that post as individuals or collaborators, and they focus on the author's experiences and/or personal reflections on events (rather than, for instance, simply reporting the views or actions of others). The persona may be fictional or real, written under a nom de plume or true name, but the perspective usually avoids bland objectivity (some news blogs are stretching this trait).
  
• One-to-many form of address. Blogs are a mass medium and are as public as the medium in which they are published (i.e., they are available to the entire Web, though not everyone has access to the Web).
  
• Serial Publication. Whether regular or irregular, frequent or infrequent, blogs are published as a sequence of postings. Topics may or may not extend across postings, either seriatim or passim.
  

Many genres share some of these characteristics; the analogues I am looking for should share all three. For instance, regular personal correspondence conveys individual perpectives and occurs as a series of communications, but it is private (one-to-one or one-to-few rather than public. Newspaper editorials are serially published and public, but they reflect corporate rather than individual or collaborative authorship. Finally, memoirs published as books typically convey a first-person perspective and are written for a public audience, but they are not serially published (except in the special case of multivolume memoirs).

So what have I missed or gotten wrong? Suggestions, especially of historical analogues to the blog, are welcome!