"You can read what they read, and see what's on their minds as they share and discuss news. Each participant has created a reading list with a feed you can subscribe to in Reader (or any other feed reader), and is also publishing shared items," says Google Reader blog.
While the ad from Google's homepage is misleading ("read what Barack Obama and John McCain are reading with Google Reader"), the idea of grouping related Google Reader shared pages could be expanded. Users could choose if they want to add their shared pages to a directory categorized based on the items that are usually shared. Google Reader could show the number of subscribers for each shared page and might even recommend shared pages related to your current subscriptions.
Sites like ReadBurner and RSSmeme let you discover people that share interesting things, but I feel that Google Reader could greatly improve this process. Shared pages act like a filter: instead of subscribing to tens of blogs about the US elections, you can subscribe to 3-4 shared pages that summarize the most interesting news and debates.
Update: Here's my shared items page and the corresponding feed. I mostly use it share blog posts about Google or technology in general, but it would be great if Google Reader added the option to separate the page in sections.