I am currently working on a recommendation system for daily news. At first, I evaluated all the recommender algorithms and their corresponding settings (e.g., similarities, factorizers, ...etc) implemented in Mahout. Since we want to recommend daily news for users, we use the reading behavior of each user collected two days ago as training set, data of the next day as the testing set. The evaluated RMSE is good, the best recommender is SVD+SGD, so we implemented the recommender on our system for several days of trial run.
However, the result, the actually recommended news, seems to be not very attractive for real users ("not attractive" here means, the users feel like "why you recommend this to me?"). So we decided another approach: use the tags and categories and their relationship to do the main job of recommendation, the result from CF is for just supporting.
This makes me wonder if CF if not appropriate for some kind of content. Because I also worked on movie and music recommendation, CF is a good tool. But for news, it seems not the case.
Can anyone explain why this happening, and also give some guideline about how to choose appropriate recommendation methods? Thanks:)