1. A computer-implemented method of predicting a target user's response to an item comprising: accessing a computer-implemented contacts service to identify at least one second user associated with the target user by the contacts service; eliciting from the second user a predicted response of the target user to the item; storing at a data structure, a second user weight for the second user; at a processor, calculating a prediction of the target user's response to the item by using the predicted response and taking into account the second user weight.