How reliable is the Pew research center?

I just gave an interview to someone from the Pew research center. I suppose that I have no way of guaranteeing that is who they are, but I did not give away personal information like credit card number or social security number, so I think it is fair to figure they are who they said they were. I initially felt good about doing the interview, but afterwards had doubts.

Who does the funding for Pew? How do they decide what questions to ask? What method do they use for selecting people? What percentage of people agree to be interviewed, and might this affect the results? The Wikipedia article on Pew said that for religious matters there is a connection to the Templeton Foundation, which did not give me a warm fuzzy feeling.