My complaint wasn't so much about the security side (I believe their claim that they won't distribute the addresses and will delete them when the survey is shut down) as the convenience side. "Fill out a survey form in 30 seconds and forget about it" vs. "submit address, wait a couple minutes, pull confirmation code out of email, go back, submit confirmation code, finally get to survey form to fill it out". Creating a disposable account would make the whole process even less quick and convenient.