I'm not terribly interested in reading what people have paid a buck to say. What would be much more interesting is an app that allowed anyone to say anything for free, and then filtered all those posts down to 20 posts for each user. So each user gets a different 20 posts, and (assuming a user posts only once a day) each user's post is seen by 20 people.

That'd be an interesting way of solving the "firehose" problem on sites like Twitter. Then, perhaps, you add on Pandora-like "thumbs up" and "thumbs down" features so that the service can pick better posts for you.