This is not true of current text export for anonymous surveys in moodle 1.8 and 1.9. Which versions (of Moodle and Questionnaire) are you using where you are getting this data? Here is an extract from a text export of a 1.9 questionnaire:
Response Submitted on: Institution Department Course Group ID Full name Username
289 15/05/2007 23:15 Questionnaire module Demo Anonymous
As you can see, the email address is not exported, ID and Username are empty and Full name is set to Anonymous.
Joseph