I’ve noticed a few new services that have replaced the traditional registration form (email/password) with email as an alternative sign-up method.
TripIt, a travel service that creates a single, readable online itinerary from your flight, hotel or rental confirmation is the first site I noticed doing this. To register, a user simply forwards a hotel, flight or rental confirmation email to email@example.com. The site automatically registers you and replies with a confirmation and link to your new itinerary. Brilliant. (Note: TripIt also provides the classic registration form as well).
What’s important about this is that they’re reducing a psychological barrier to entry. Most people using Flickr, Facebook, LinkedIn, Gmail, etc. feel signing up for yet another online service is an annoyance. After a while, another registration form can feel like a burden. Email-based registration avoids this barrier by rolling registration and the way you interact with the service into one action. For example, the same way you use TripIt is the same way you sign up, by forwarding emails to firstname.lastname@example.org.
Of course, form-less registration doesn’t fit for every solution. While flushing out the IA for ImageSpark, our home-brewed creative inspiration tool, we decided upon the classic email/password registration. The reason being that the core interaction with the site isn’t done through email but rather integrated browser and desktop upload tools; For ImageSpark, there was no gain in baking in an email-based registration. (Although we hope this won’t stop people from using it.)
A service like Posterous however, which uses email to create and update a blog, is built on avoiding forms at all costs. It makes sense than that your first email registers you and initiates your first blog post, all in one.
I’m pretty sure we’ll see form-less registration grow into a design pattern as new services emerge. And I’m looking forward to using it, so long as the situation is right.