How do I disable Bonjour visibility after Yosemite install?
There is no more com.apple.mDNSResponder.plist in OS X 10.10.  The service that controls mDNSResponder is now discoverd. The plist file you are looking for is actually: 

/System/Library/LaunchDaemons/com.apple.discoveryd.plist


You want to add --no-multicast to the ProgramArguments in that file.  

    &lt;key&gt;ProgramArguments&lt;/key&gt;
    &lt;array&gt;
            &lt;string&gt;/usr/libexec/discoveryd&lt;/string&gt;
            &lt;string&gt;--udsocket&lt;/string&gt;
            &lt;string&gt;standard&lt;/string&gt;
            &lt;string&gt;--loglevel&lt;/string&gt;
            &lt;string&gt;Basic&lt;/string&gt;
            &lt;string&gt;--logclass&lt;/string&gt;
            &lt;string&gt;Everything&lt;/string&gt;
            &lt;string&gt;--logto&lt;/string&gt;
            &lt;string&gt;asl&lt;/string&gt;
    &lt;/array&gt;


Becomes

    &lt;key&gt;ProgramArguments&lt;/key&gt;
    &lt;array&gt;
            &lt;string&gt;/usr/libexec/discoveryd&lt;/string&gt;
            &lt;string&gt;--udsocket&lt;/string&gt;
            &lt;string&gt;standard&lt;/string&gt;
            &lt;string&gt;--loglevel&lt;/string&gt;
            &lt;string&gt;Basic&lt;/string&gt;
            &lt;string&gt;--logclass&lt;/string&gt;
            &lt;string&gt;Everything&lt;/string&gt;
            &lt;string&gt;--logto&lt;/string&gt;
            &lt;string&gt;asl&lt;/string&gt;
            &lt;string&gt;--no-multicast&lt;/string&gt;
    &lt;/array&gt;


You'll want to be very careful when editing that file. You can also use this script to do it for you - https://raw.githubusercontent.com/MacMiniVault/Mac-Scripts/master/disablebonjour/disablebonjour.sh