Making OS X Lion use search paths.

Apple changed the behavior of DNS search list processing in Lion (OS X Lion: About search domains and name lookups). 

This makes it differ from the behavior listed in RFC1536. If you need / prefer the RFC-compliant search path processing, add the -AlwaysAppendSearchDomains argument to the /usr/sbin/mDNSResponder process in /System/Library/LaunchDaemons/com.apple.mDNSResponder.plist

So:

            <key>ProgramArguments</key>
        <array>
                <string>/usr/sbin/mDNSResponder</string>
                <string>-launchd</string>
                <string>-AlwaysAppendSearchDomains</string>
                <string>-NoMulticastAdvertisements</string>
        </array>

Additional information