authority

This fallacy is also called "Argumentum ad Populum". This is when someone tries to make their argument based on the fact that it is a popular choice among people, or what most people believe. It is an extension of the Faulty Appeal to Authority. If it is wrong to appeal to one person who is not a legitimate authority on a subject, then it is just as wrong to appeal to multiple people who are also not experts on the subject. 

We defer to all kinds of experts in our lives.  When we are not feeling well, we go to the doctor.  When our car starts to blow smoke and the engine is running rough, we go to a mechanic. Generally, we follow the advice of these experts in their fields because they know more than we do. That makes good sense. But what if we asked our mechanic about our health issues and our doctor about our car troubles? Would you trust them implicitly and take their advice? Perhaps we shouldn't.