Feedburner published a post research today noting that Google Reader is the clear leader in the feed reader group. WebmasterWorld recently highlighted a new Google patent which relies on user input to demote spam:
The system may aggregate information regarding documents that have been removed by a group of users and assign scores to a set of documents based on the aggregated information.
The WebmasterWorld thread also highlighted that AdWords advertisers and AdSense publishers might highlight some of the bad documents. The patent application also mentions determining which users should be trusted.