Just like .bind, .delegate (and .live) should accept false as a shortcut for function(){return false;}.

That way, someone could just do something like this to stop the original .live selector from matching just the "a" elements, instead of having to write a huge, complicated patch. :P

$('a,form').live( 'click', fn ); // pre-existing code

$('body').delegate( 'a', 'click', false ); // their code