[Air-l] response rates to pop-up surveys on health issues

Hi all Does anyone have any references to papers which have surveyed health users (particularly users of health virtual communities) using pop-ups, and calculated response/recruitment rates? Or has anyone conducted such a survey themself? I want to compare the recruitment rate in my study with those found in other similar research. Many thanks! John Dr John Powell Clinical Research Fellow London School of Hygiene & Tropical Medicine john.powell@lshtm.ac.uk