Well, no surprise this was down voted since most people in this thread never seems to have worked in this field. I have worked with recommendations on a service

Well, no surprise this was down voted since most people in this thread never seems to have worked in this field. I have worked with recommendations on a service with millions of users. We do not guess. We look at things like conversion rates to tell us what works. If one think down votes would play a significant part in training a model you simple does not understand the amount of metrics a modern service collects and what impact different variables have.