I work for a company that actually runs surveys, and believe me: we don't know who the respondents are. They get a link with a randomly generated id, and that's

I work for a company that actually runs surveys, and believe me: we don't know who the respondents are. They get a link with a randomly generated id, and that's it. For us, even their email address is hidden, because respondents register to panel at another company, which deletes this information three months after closing the survey, which usually runs for a few days. I can't vouch for the other company, of course, but I do believe them. Sometimes it would be really nice to know who these people are, because not only is non-response a problem, bad responses are an even greater problem, so we'd like to know who to exclude in advance. So much for unbiased representation.