Actually, our perception of χρονος - is an inheritance of the Greco-Roman culture: linearity going from somewhere (usually in our mind from left) to somewhere (toward the right side). As I said, it's a characteristic of the Western culture, all related to the Greek way of thinking based on syllogism, the linearity of the time and, quite importantly, the phonetic alphabet with its own linearity... N.B. form left to right :)
The way the blog displays posts doesn't really have to do anything with our perception of the time - it's more a practical one. If you have dispayed 24 posts on your main page and the oldest on the top (according to your "classical" chronological order) then for every new post I have to scroll down, or worst - in case of the 123th post - click next page and next page and next page... until I get to the newest post.
I'd never read your blog if it requires this exercise to get the latest update. However, with the "blog-like" chronology, I always get your last post on the top, exactly what I need to keep up with your travel.
Don't think of a blog as a book (conf. linear, left-to-right time line!) - it's a different media!
(finally, don't think I am a teenager blogger... on that time line I am much closer to you than you think :)
p.s. Oh, and if something is not clear in the above text: I am not a native English speaker.