The Permanence and Reliability of Blogs as Sources

Blogs are easy to change.  Podcasts are not.  It's essentially a software tool issue ... with the evolution of CMS systems like Typepad, it's easy for me to update my blog - change categories, design and layout (apologies to those of you who have suffered through my recent experimentation with the "Masala" template - but I'm back to my original design with some minor tweaks).  Podcasts are much tougher, with more in-depth audio splicing/editing skills required.  The ease with which blogs can be updated brings up a question about the wisdom of using such an evolving medium as a source in journalism, research, or even in cross linking.  No one would suggest using a landmark of a person sitting at a coffee shop to give directions on how to get somewhere.  Yet using blogs, which some would describe as nothing more than microcosms of opinion fashioned into a format that is increasingly being treated as fact, raises a whole new credibility issue. 

It comes back to the rise of the "citizen journalist" and the fact that this term elevates blogging beyond just a collection of ranting and raving from the informed/ill-informed masses (particularly in the realm of "professional" blogs).  Can a blog post be treated as a reliable source?  And as a blogger, is it ethical to change a blog post once it has been posted?  Does it just come down to each individual blogger's own personal code of conduct, or will the blogosphere begin to set it's own standard over time?  The concept of a "self-policing" set of accepted values about blogging (beyond any one corporation's blogging rules) will be an interesting development to watch.  Perhaps the next step is a W3C-style body which publishes a journalistic baseline which bloggers can choose to follow or ignore.