Ideas: wiki, bookmarks, blog, and life stream all merged into one.
"Heavy" normal blog articles.
Bookmarks/links, ala Delicious. Should be able to pull a thumbnail when posting (like Facebook), and cross post onto other sites.
Photos, the minimum of which would just be posting a link to Flickr and automatically pulling photo, title, and description.
Videos. Post a YouTube or Vimeo ID and automatically do an embed, or upload my own video and display with local HTML5 player.
Location/Maps. Post a link to an address, OpenStreetMap feature, or lat/long coords.
Should be WikiWikiWeb-style pages that automatically update themselves as new posts are added.
Should be able to create arbitrary topic pages that display combined tags, i.e. have a page for "Linux Software" that pulls from the "Linux" and "Software" tag/topics.
Done via Pingbacks, Trackbacks, (i.e. people go write their own blog post), and OStatus (not exactly sure how that'd work… piggy back on Pingback or Trackback?).
"Feedback" section has tabs, Comments, Trackbacks, Merged.