It's definitely the underscore: <a href="http://usesthis.com/" rel="nofollow">http://usesthis.com/</a> is accessible, as are all the other interviews, but <a href="http://_why.usesthis.com/" rel="nofollow">http://_why.usesthis.com/</a> isn't.<p>And it doesn't seem to be the browser's fault:<p><pre><code>  $ ping richard.stallman.usesthis.com
  PING richard.stallman.usesthis.com (74.207.245.100) 56(84) bytes of data.
  64 bytes from waferbaby.com (74.207.245.100): icmp_seq=1 ttl=51 time=63.6 ms

  $ ping _why.usesthis.com
  ping: unknown host _why.usesthis.com
</code></pre>
So I can't resolve the domain name for some reason.  This happens on both my home Gentoo box and my Slicehost Gentoo server.