Very high potential for the respondent to corrupt survey by deleting brackets. Very prone to processing errors once the e-mails are returned to administrator. Respondents view e-mail text surveys as very unprofessional or antiquated. There's a lot more, but we think you get the message about e-mail based surveys. The main problem here is losing respondents.
Many respondents simply give up and fail to complete the survey.
Inherent web server delays causing the respondent to give up. Potential to confuse cgi by using Back Button rather than a link on survey page. Not all Java script is created equal. There are differences in implementation among browsers and among versions of browsers. In order to ensure correctness of execution on all the different browsers, an HTML survey using Java script should be tested on each of the possible browsers.