function init() {
    new Insertion.Bottom(document.body, '<span id="mySpan">Leak free</span>');
    var span = $('mySpan');
    //does not leak any more
    span.onclick = function(evt) {alert(this.innerHTML);}.bindAsEventListener(span);
    //does not leak any more
    var mouseoverHandler = function() {
         //this will point to span
        $(this.setStyle({backgroudColor: 'green'});
    };
    Event.observe(span, 'mouseover', mouseoverHandler);
}

//Leak free event observation patch for Prototype
//Written by Arrix, 2006-08-24 17:15:55 GMT+0800 
//with input from Ross and Laurens
//
//Fixes and features:
//* Fix IE memory leak when bound nested functions are used as event handlers. bind() and bindAsEventListener() now use leak free closure
//* Fix IE memory leak when an unbound function is passed to Event.observe()
//* In IE, this pointer now points to the element being ebserved inside an unbound observer(this use to always point to the window object in IE)
//* Mixed Ross's fast load solution in. Observers to window's load event are triggered right after the document finishes loading
//http://www.agileweb.org/articles/2006/06/26/speeding-up-onload-update
//http://www.agileweb.org/articles/2006/07/28/onload-final-update
//http://laurens.vd.oever.nl/weblog/items2005/closures/
Object.extend(Event, {
    _observeAndCache: function(element, name, observer, useCapture) {
        if (!this.observers) this.observers = [];
        var i = Event.observers.length;
        //CAUTION: DO NOT bind window as this pointer in IE
        //this pointer inside an event handler always points to the window object if the event handler is attached using IE's attachEvent() function
        var wrapper = function() {var thisObj = this === window && navigator.appVersion.match(/\bMSIE\b/) ? null : this; Event.observers[i][2].apply(thisObj || Event.observers[i][0], arguments);};
        if (element.addEventListener) {
         this.observers.push([element, name, observer, useCapture]);
         element.addEventListener(name, wrapper, useCapture);
        } else if (element.attachEvent) {
         this.observers.push([element, name, observer, useCapture]);
         element.attachEvent('on' + name, wrapper);
        }
        element = observer = wrapper = null;
    },
    
    observe: function(element, name, observer, useCapture) {
        element = $(element);
        useCapture = useCapture || false;
        
        if (name == 'keypress' &&
            (navigator.appVersion.match(/Konqueror|Safari|KHTML/)
            || element.attachEvent))
         name = 'keydown';
         
        if (name == 'load' && element.screen) {
         this._observeLoad(element, name, observer, useCapture);
         return;
    }
    //Assuming that browsers which support DOM2 event model do not have the memory leak problem, we don't need to _observeAndCache()
    if 
        element.addEventListener(name, observer, useCapture);
        return;
    }
    
    Event._observeAndCache(element, name, observer, useCapture);
    },
    _observeLoad : function(element, name, observer, useCapture) {
        if (!this._readyCallbacks) {
         var loader = this._onloadWindow.bind(this);
         if (document.addEventListener)
             document.addEventListener("DOMContentLoaded", loader, false);
         //conditional comment will be stripped by custom_rhino, we use browser detection instead
    //     /*@cc_on @*/
    //     /*@if (@_win32)
    //         if (! $("__ie_onload")) {
    //            document.write("<script id='__ie_onload' defer='true' src='://'><\/script>");
    //            var script = $("__ie_onload");
    //            script.onreadystatechange = function() { if (this.readyState == "complete") loader(); };
    //        } else {
    //            loader();
    //        }
    //     /*@end @*/
         if (navigator.appVersion.match(/\bMSIE\b/)) {
            if (! $("__ie_onload")) {
                document.write("<script id='__ie_onload' defer='true' src='://'><\/script>");
                var script = $("__ie_onload");
                script.onreadystatechange = function() { if (this.readyState == "complete") loader(); };
            } else {
                loader();
            }
         }
         if (navigator.appVersion.match(/Konqueror|Safari|KHTML/i))
            Event._timer = setInterval(function() {if (/loaded|complete/.test(document.readyState))loader();}, 10);
         Event._readyCallbacks = [];
         this._observeAndCache(element, name, loader, useCapture);
        }
        Event._readyCallbacks.push(observer);
    },
    _onloadWindow : function() {
        if (arguments.callee.done) return;
        arguments.callee.done = true;
        if (this._timer) clearInterval(this._timer);
        this._readyCallbacks.each(function(f) { f() });
        this._readyCallbacks = null;
    }
});
//Leak free bind
Function.prototype.bind = function() {
    var __method = this, args = $A(arguments), object = args.shift();
    return function() {
    return __method.apply(object, args.concat($A(arguments)));
    }.zm_closure();
};
Function.prototype.bindAsEventListener = function(object) {
    var __method = this, args = $A(arguments), object = args.shift();
    return function(event) {
    return __method.apply(object, [( event || window.event)].concat(args).concat($A(arguments)));
    }.zm_closure();
};
//zm_ is simply a prefix used in my project to avoid naming conflicts
Function.prototype.zm_closure = function()
{
    if (!window.__funs) window.__funs = [];
    var fun = this;
    var funId = this.__funId;
    if (!funId) __funs[funId = fun.__funId = __funs.length] = fun;
    fun = null;
    return function ()
    {
    return __funs[funId].apply(null, arguments);
    };
};