Qualified subjects are offered rewards and prizes for completing surveys. Won't work though for some populations. Cheap , less effort to reach random samples. Rapid to administer from a central location. Bias and lack of rapport.
Survey research is incredibly dependent on credible samples.
We have discussed various sampling methods, methods of gathering and bias inducing questions. However, you may not have thought about this. Many firms hire young people, folks on the edge of society or people or who are broke. They are paid minimum wage plus a commission if they complete an interview. Thus, they are under tremendous pressure to complete a survey.