You wrote: "people in the future will subscribe via RSS."
You don't have to wait for the future... Come take a look at the service we provide at http://weblogs.pubsub.com/. We monitor over 1.1 million weblogs in realtime and allow people to create persistent queries or subscriptions that select from all the blog updates just those they are interested in. Items that match a users subscription are then inserted into a custom RSS feed for them.
Using a system like this, you can decide that you want to see all items that contain references to some specific subject and then our real-time matching engine will build you precisely the feed you are looking for. Similarly, a business can create a new blog entry and know that everyone who has a subscription to some keywords in that entry is going to see it in their personal feeds.
This is called "content-based" publish and subscribe. i.e. Your subscription selects items based on their content, not who wrote them or where they were published.
Come to http://pubsub.com/ and give it a try!

bob wyman