The format of the output is somewhat less important, although I just seem to think RSS feeds are a inherently superior way to get content than a list of links.

The format of the output is somewhat less important, although I just seem to think RSS feeds are a inherently superior way to get content than a list of links. The INPUT on the other hand is extremely important. Take a look at Reddit... you have to manually up/down vote articles to make the recommendation system go. Not only is that tedious, but I don't believe people actually have a good grasp of the content they are looking for. RSS feeds, on the other hand, are much more relevant. And getting a list of someone's feeds requires no work on their part to describe to you their interests. Even better, online readers/aggregators such as Google Reader have an even more extreme advantage in being able to tell what you read and how often you read it (as the other poster pointed out) more accurately than your OPML file. It's a gold mine for anyone trying to build content recommendation systems. Take a look at Reddit... it's become a collective RSS feed aggregator plus stupid pictures of cats. If the recommendation engine worked, it would be a GOOD collective RSS feed aggregator. I believe you can get there by working with RSS feeds and actual reading statistics as inputs rather than manual link clicking.