Human Clock

I just got turned on to HumanClock. Gotta love it, very creative, without being pushy. Thanks to Seth Godin for the link.By the way, whatever happened to Collaborative Filtering? It's a filter based on the simple observation that people with similar preferences will tend to be interested in the same things. Is it something that has only migrated into personalization systems like's book recommendation system? Or is it an idea that has fallen out of favor? Sure, there are some problems, namely, that someone has to be on your site long enough for you to get an idea of their preferences. But I think that the idea is still largely untapped.