a "valid" email address is a laudable idea...but anyone can get a valid email address in 5 minutes (hotmail, [email protected], [email protected], etc.)

so you'd have to make it a "real" email address (eBay does this, by maintaining a database of free email companies and not letting folks register with theese types of addresses).

But as Rudi points out, this would violate the privacy of a lot of people (not just the ladies) and turn off a lot of people.

It just gets very complicated and ends up serving no real purpose.