Sad Nat was created in December 2010 by Nat Welch when he thought it would be better to send a URL than an emoticon. For a year, sadnat.com was just a static page. In November 2011, David Patierno convinced Nat to make the site dynamic, and together they did so in one day.
The sadnat picture is blatently stolen from Octopus Pie.
You can file bugs, complaints and feature requests either on github or by emailing email@example.com.
There are 125 entries.