My preference is that there are two required dates: one subjective and indicative of what you see with blogger and livejournal, another objective and machine generated:
http://www.intertwingly.net/blog/1504.html
To date, these have been assumed to be the <issued> and <modified> dates.
This leaves the <created> as the odd man out. While I don't see a strong need for this, if a number of implementations track this data and would like to express it in a consistent manner, it makes sense to standardize it.
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