10. The computer program product of claim 7 , wherein training the predictive model includes dividing the online activity data into first and second portions and using the first portion to train the predictive model, and wherein identifying the cross product involves applying the trained model to the second portion.
10. The computer program product of claim 7 , wherein training the predictive model includes dividing the online activity data into first and second portions and using the first portion to train the predictive model, and wherein identifying the cross product involves applying the trained model to the second portion. 11. The computer program product of claim 10 , further comprising ranking at least some of the characteristics with regard to the interaction proneness, wherein the ranking is taken into account in distributing the content item.