What this writer is lamenting does not in my opinion signify the death of opinion journalism--existenial or otherwise. It does illustrate several other characteristics of the nature of journalism and politics in an era of spin, complacency and disillusionment which remain constant no matter what form of media is being analyzed:
The quality of any discussion is equal to the capabilities and knowledge base of the participants.
Just because the internet is new that doesn't mean that the way it has been applied as a mode of advertisement/communications/self-aggrandizement/mud slinging by people in politics will change. Its political users still want to beat their opponents by all means and the suppliers, bloggers and ezines (once mainstreamed), want to get paid--apparently at costs--moral, spiritual, philosophical...... Established politicians had a learning curve when it came to the internet--but Howard Dean fixed that.
Every mode of communication has the possibility of being co-opted, writers and others need to decide for themselves whether or not they wish to participate. Brendan Nyhan decided not to participate.
I return to my first point. If the participants, journalists, publishers and readers want a better or different quality of opinion journalism at profit, it's going to require a little ingenuity and a whole lot of fortitude.
As for the business of non-partisian opinion journalism, all business models must adapt and from Brendan's article, I'd say it's time for non-partisian opinion publications to get a brand new bag.