Update 6-May-2008: Okay folks. Some wags have been entering their emails twice, as comments to this post. It remains my most commented post after almost a year, but I've been deleting many comments as spam. I'll let you play the game if you post substantive comments in addition to your email addresses. Thanks!
To the left is a thumbnail of the Massachusetts Registry of Motor Vehicles website, registration renewal form. (It's linked to a pop-up full size version.) I visited today and ran into one of my pet online peeves.
Enter E-mail Address:
Enter E-mail Address Again (for verification):
Note: You must provide a valid E-mail address to receive a receipt for this transaction.
I'm baffled why many sites force people to type their emails out twice. Do they think it will prevent mistakes? That's the reason to enter password twice. If the password you create looks like ******** in the field, you might make a typo without realizing it and not be able to log back in. So double password entry makes sense. But when you see your email address as you enter it, you can correct mistakes like you would with anything else you type into a computer.
I honestly don't know why sites design in double email fields, but my guess is it's meant to discourage users from entering something bogus. It may or may not be effective, but it's a lame technique that slows people down. You're missing an opportunity to build trust by telling users the value you bring them. If email address really is important, simply communicate why to your users. For example:
Enter E-mail Address:
We will send your receipt to your email address above.
The supporting text provides enough contextual info so that users see the value of entering a real email address.
If email address really doesn't provide any value to users, only to your marketing department, get used to people quitting your workflow or entering junk. In usability tests of consumers, I find concerns about spam and their personal info to be among the most frequent unsolicited comments about an interface. It takes communicated value to overcome their resistance and build trust.