Recommendation Systems in Social Media

Muhammad Saleem has done a nice write up of how consumer social media sites are using Collaborative Filtering over on Read/Write Web.

The only thing I disagree with is equating Collaborative Filtering with Online Recommendations. Collaborative Filtering is only one technique that one could use to provide recommendations.CF is a good tool but you have to be careful to apply the right tool to the right situation.

At Aggregate Knowledge we actually use a variety of different algorithms types to determine what someone might be interested in. For example taking into account seasonality, recency/frequency and lexical matches to show you things you're most likely to want to see.