Making your website more personal has long been a wish for many developers. If you can predict what your visitors will like, you could give this content a more prominent position and potentially increase participation (clicks, sales, uploads, comments, ...) on your website.
The power behind the generation of personalized suggestions is the recommender system. Something magical that comes in many flavors and has many uses... The magic part is that it's very difficult to accurately anticipate the wishes of your visitor... However, it is not impossible.