(reviving an old draft)
A blog shouldn't be a series of posts. What if I want to change an older post?
A blog should be a graph of posts, and the "chronology" should be a series of diffs, some of which are entirely new posts, and the rest are modifications to earlier posts.
The chronology is just one of many views of this graph though, it should be possible to view a personalized "recently viewed", "recommended", "random tag/category", etc.
What is special about a blog anyway? Isn't it just a nested collection with different kinds of tags?