If you look at the fundamental reader benefits (the reasons why we want to access the content), you have to lump blogs in with feeds. Sure, as delivery vehicles they are different, but they both deliver the same thing. The differences between delivery technologies don't matter so much as the differences between the intrinsic nature of blogging and the intrinsic nature of discussion groups. That's all about content, context, human interaction, and less about whether it's a push or a pull mechanism.
In the 'discussion blogs' that I am involved with (such as InternetTime or LearningCircuits) the nature and range of discussion is hampered by the technology, and has to stay issue focused, and only those of us who have the authorization can initiate threads. Even with a huge number of 'readers' every day, it is rare to see more than three or four comments in a thread.
Blog authors are often better than a search engine, in that they act as a credible guide to Web content that is specific to their context or area of interest. Search engines scan tags, content, and links; blog authors use more helpful human dimensions such as context and quality by which to evaluate relevance.
Discussion lists are not always push. I have never used discussion lists such as trdev as push -- and I am amazed that so many people still use them that way. How many e-mails per day can you actually deal with?? I visit trdev on the Web every day, and can see at a glance subjects and authors of recent posts. I read -- online -- only those posts that interest me, and reply using the online system. So discussion lists are pull for me, not push, where that option is available. If an online site is not available, I get a daily digest rather than the individual e-mails -- but I confess I rarely scan more than the topic list, hardly ever read the posts, and almost never respond. The technology just makes it less accessible for me.
I spend less time on discussion forums these days because the quality, relevance, and accessibility of information available to me via selected blogs is orders of magnitude better than anything I ever derived from participation in those discussion forums.
I think that as the Internet and its users become more sophisticated, they fragment into smaller more homogeneous clusters. With hundreds of millions of users out there, why should trainers all come to trdev when there may be a smaller more targeted discussion group that is more relevant ('sales trainers in the consumer goods field in Ireland' for example)? As far as I am aware nobody is creating those communities using discussion forums or lists -- but bloggers ARE coming close. A blog requires a champion around whom like-minded people can start to crystallize into a community; once that community has some kind of critical mass, they are going to want a better vehicle for networked communication. Which is where I think social networking software may come into its own.
I do think that 'the old way' of doing things on the Internet is increasingly time-consuming and decreasingly relevant. But it's 'the old way' that is at fault, not the ever-expanding Internet :-).