Is it just me or is Google DNS not resolving .us domains?

Google's DNS servers (8.8.8.8, 8.8.4.4) seem to not be resolving .us domains. Is anyone else having this issue? If so, why is it happening?

Google

nslookup about.us 8.8.8.8

Server: 8.8.8.8

Address: 8.8.8.8#53

server can't find about.us: NXDOMAIN

OpenDNS

nslookup about.us 208.67.222.222

Server: 208.67.222.222

Address: 208.67.222.222#53

Non-authoritative answer:

Name: about.us

Address: 156.154.193.226

Name: about.us

Address: 156.154.42.226