I think intranets will be with us for a while yet based simply on the scale of infrastructure and investment that’s gone into them.
I also believe that on any given intranet, even before the advent of social media, 50% of the content and even interface/IA is actually “dead” — if not “DOA” because of intranet management, governance and politics issues.
With the social media and user-generated content trend (or is it a movement? or a sea change?), I’d say intranets as we know them are now … 75% dead.
I don’t think intranets are bad. I think they are good. Some are great. (very few). In my experience of more than 60 private and public sector intranets, though, 95% of them are ready and effective for the company … as it was 3 years ago…