While multiple responses may be acceptable for American Idol, serious survey research dictates that we try to prevent people from responding multiple times to a survey.  In addition, when asking about specific events we need to ensure that the correct individual is responding. There is an increasing use of Web-based surveys for both of these activities. Survey researchers are increasingly using multi-mode surveys, one of which is Web-based, to increase response rates; and corporations are using Web surveys as an inexpensive way for obtaining consumer feedback. Both these applications require authenticating the respondent to ensure that they have not responded previously to the survey or that they have obtained the service.