Yes, agreed (and I mention this at the end of the article as well) and I still use the /@/ regex often. But a good UI on the registration form can go a long way in alleviating the "switching the email address and username fields" problem.

>a good UI on the registration form can go a long way in alleviating //

But not all the way. And so a simple "you might have got this wrong" flag would be helpful, no?

"You might have it wrong", yes. "You are wrong, we won't let you submit the form" won't.

One addtional check---see if there's an MX or an A record on the portion after the "@".