Recent versions of Ghostery (and NoScript) both provide 'surrogate scripts' to replace common JS resources that are expected to work by the active page.

You can see the noscript[1] ones at about:config (search for noscript.surrogate.*) but I'm not sure where the Ghostery ones live, or if it has specific ones for different trackers, or just a generic handler.

[1] GA replacement code appears to be (reformatted):

    (
    function(){
        var _0 = function(){
            return _0;
        };
    
        _0.__noSuchMethod__=_0;
    
        with (window) urchinTracker=_0, _gaq={
            __noSuchMethod__: _0,
            push:function(f){
                if(typeof f=='function') f()
            },
            _link:function(h){
                if(h) location.href=h
            },
            _linkByPost:function(){ return true },
            _getLinkerUrl:function(u){ return u },
            _trackEvent:_0
        }, _gat={
            __noSuchMethod__:function(){ return _gaq }
        }
    }
    )()