It is a good idea mate I've thought of that myself a few times but there are a lot of people who really don't understand the basics of computers let alone signing up to a forum and asking a question.
You wouldn't believe the amount of emails I get on questions about patrols or how do I ask a question, sign up, manuals etc.
I'm trying to make it as easy as possible for people to sign up and ask a question and that extra restriction may be too much for the average joe.