I pretty sure Ed meant Wordpress.com not .org
Basically the reason for WPD as to Wordpress.org is
that the 30DC consist of a good share of newbies
that would be greatly held back with the main
focus of the 30DC training trying to also learn
installing a WP blog.
WPD makes getting your blog up with all the plugins
(already configured) quick and easy, where as using
a self hosted WP blog (Wordpress.org) requires setting up
and maintaining yourself which for the new and non
techie can be a challenge in itself and would require
a 30day course alone.
You can use Wordpress.org (self hosted/maintained)
if you want and have the tech nohow WPD is not mandatory
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