Ask HN: Good examples of registration ui

I did some searching and found this link: http://ui-patterns.com/explore/collections/account-registration

It has some good examples but I wanted to hear your opinions on what works and what doesn't. I personally like HN and Instapaper's simple registration forms and was wondering why there aren't more services using similar sign up forms. Wouldn't having one field for an email address and collecting all of the other cruft after validation be easier for end users?