you intend to contact people who respond to the survey, make
sure you get their contact information. In other words, ask for
the contact information in a question (or two).
if your hosted survey provider allows for by-invitation-only
surveys, you may be able to avoid asking for the contact information
in the survey itself. Papaya Polls is able to provide this
feature; however, we still recommend that survey designers ask
for the survey respondent's contact information because email addresses
and other information is prone to become out of date over time,
and it gives a fair notice to the survey respondent that they may
be contacted in the future.