Adina Levin just posted a concise summary on how wikis, weblogs and RSS are the next step in enterprise portals:
Corporations still need "home pages" to provide a shared set of starting points and departure paths. But the portal isn't the tool that publishes the content or manages the data aggregation. The publishing and subscription processes are being radically decentralized by the use of wikis, weblogs and RSS.
I'd add that Portals simply suffer from feedback deficit disorder (FDD).