I'll try to make a point that I had in my head while I was writing my ramble. In the forum case, the method of finding interesting persons is to go where they are. It's the same mechanism that drives the crowds to popular clubs and pubs - people want to be where it's cool to be. That will lower the percentage of cool people there in that place, and the cool people will move on to the next place. The clubs try to counter this by having guest lists and bouncers that only let you in if you're cool enough (that's not an easy thing to do online).

In the RSS case, you're not trying to find cool people by going to their favourite place, instead you go to their homes. Which is all nice and well, except you have another problem: how do you find out where the cool people live? Especially if you get all your input from the world through the RSS feeds, you're well on your way to getting a very limited view of the world (sort of like only watching Fox News, or one of the other more or less biased news outlets). Your RSS sources will act as gate keepers by only linking to what they find interesting, which can lead to a narrowing spiral.

In short: RSS is very useful, but make sure you're not only listening to a single subset of opinions. To prevent this I do what I suspect what most people here do: I keep track of my favourites using RSS and look for new stuff on HN, Reddit, etc.