A journalist is someone who gets paid to report on things that happen. Journalists are supposed to use facts to represent an accurate reflection of history and provide an objective account of those events.
A blogger is someone who typically is not paid to publish their thoughts, and they do so via any number of freely available websites as a platform to deliver those thoughts. Objectivity is not considered a requirement, and bloggers often eschew objectivity for the sake of offering an opinion.
Except that many bloggers do get paid to write, and journalists don't always provide a factual or even objective editorial on events.
I think that blogging, as well as video and audio podcasting, becomes a skill in itself. Enthusiasts will create content about subjects they are familiar with, but the tool they use - blog sites, camera phones, amateur camcorders, production software - all of these elements begin to collate and manifest themselves in a broader ability to communicate. Of course they would! That's the point. But the content that bloggers create is not limited to what they know. In the exploration of delivering home-brew media to the Internet, with potentially millions of content consumers, they now understand how to deliver it. They may find their voice, and it may have more than a single dimension of dialogue.
And as bloggers begin to make some money (or, monetize, if you prefer, though I'm not sure if that term has fallen into the language-meme graveyard yet, to join the ranks of dot-com bubble words such as "synergy" and "paradigm") they enter into the competitive market of people-who-write-shit-so-others-will-read-it. And they can take that new skill and apply it to anything they have an opinion on. Some of the more popular bloggers (as well as podcasters and even Machinima makers) even publish collection of their work and sell them for profit.
The difference then becomes exactly how you make money. Are you working for a large, established publisher like Rupert Murdoch? Then you're likely a journalist. If you are independent, or a member of some startup Internet media company like Gawker or Revision3? Probably a blogger.
I believe that if Hunter S. Thompson (who wrote about drug culture, politics and sports) started his career today, he would have been a blogger. And we;d be better off for it.