I seldom believe questionnaire surveys.
There are lots of such surveys published on newspapers, magazines, and also internet. But in my opinion, almost all articles are far beyond the fact. The reason is that they do not define the target.
Every survey has a goal. In a questionnaire survey, we should decide the subject. The unique condition of the subject is that we would be able to know the fact with the data gathered from this subject. They require to represent the real target we want to pick up. If this condition were not adhered, the result of the questionnaire would be useless.
Most public surveys do not meet this criterion. Thus, they are pointless.
For example, a popular newspaper investigated the tendency of the readers regarding the policy. A writer asked for the reply via the internet. So many responses had come. The writer summarized the data with pleasure. As a result, most of the readers were revealed to have an aggressive thoughts in the policy making.
This process includes a fatal error. Persons who are willing to reply to the survey tend to be concerned with the policy making. Therefore, the majority of the respondents seemed to be aggressive. However, the vast majority of the readers did not respond this questionnaire. After all, the total image of the readers could not be proven.
This is an issue so called 'Silent majority'. There are lots of similar situations. Some social network services are filled with dirty words. But it does not mean that the users of the internet are impolite. The fact is that polite persons avoid leaving a comment on such a board. Also, several surveys showed the fact that consumers want low calorie hamburgers. However, there are almost no popular low calorie hamburgers. That is, the vast majority of hamburger lovers dare not to answer the questionnaire. And they are fond of oil-rich one.
As a researcher, I have experienced to conduct several questionnaire surveys. I Always struggle to define the target, and attempt to gather all responses of the targeted subjects. This is the most difficult point to perform a qualified survey. As I know its difficulty, I hardly trust this kind of surveys.