Designing for social traction: Turn a user into a passionate customer *before* making them sign up for your service – Sachin’s Posterous

But sign-up free posting is also great for group sites. When you setup a group Posterous site, you add contributors by adding their email address in site settings. Those people can now email post@sitename.posterous.com with no account. We do see these people engage with Posterous in the long term with no account, especially users who aren’t tech savvy.

Using Posterous without an account isn’t just some gimmick we did with email, it’s something we believe in through and through. Registrations forms and other hurdles slow down adoption. We want to prove to you how valuable our service is before we ask you to sign up. That’s why we allow this flow not just through email, but through our Twitter posting API and even our iPhone application.