Well, how often do people sign up with a different e-mail address (especially the target group of parents and seniors)? You should measure this. Only solve it w

Well, how often do people sign up with a different e-mail address (especially the target group of parents and seniors)? You should measure this. Only solve it when it becomes a real problem. I used to think like this as well, but you're basically falling in the trap of sacrificing usability for 95% while you solve the problem for the minority of 5%. Let's say your conversion rates drop by 25% because you have this hurdle. In an attempt to save the 5%, you're now at a net loss of 20%.