gistfile1.js

(function(){
	function focusInHandler(e){
		Event.findElement(e).fire("focus:in");
	}
	function focusOutHandler(e){
		Event.findElement(e).fire("focus:out");
	}

	if (document.addEventListener){
		document.addEventListener("focus", focusInHandler, true);
		document.addEventListener("blur", focusOutHandler, true);
	} else {
		document.observe("focusin", focusInHandler);
		document.observe("focusout", focusOutHandler);
	}
})();
document.on('focus:in', selector, function(){
	// on focus 
});
document.on('focus:out', selector, function(){
	// on blur
});

In this case Event.element(e) === Event.findElement(e) but executes slightly faster (in fact findElement with single argument directly calls Event.element)

yes currently, but Event.element is going to be deprecated and removed in the future. Because and thats the reason for this change.

Deprecated? Maybe. Removed? Deprecated things like Element.ClassNames, Position, $continue, Insertion, Toggle are still not removed. Why such widely used (e.g. in scriptaculous, ajaxtags, livepipe, modalbox, tablekit) method like Event.element will be removed in the (near) future?

I don't know from the docs - http://api.prototypejs.org/dom/event/prototype/element/ and from I have communicated with the Prototype Core it will be removed some day. Prototype as a whole is moving really really slow :( But I prefer my code to use the no deprecated funcs. (as for ClassNames, Position, $continue, Insertation, Toggle I use a custom build and not include those)