gistfile1.js

$H(Element.Storage).inject(0, function(m, p){
    var registry;
    if (p.value.get && (registry = p.value.get('prototype_event_registry'))){
        m += registry.values().flatten().size();
    }
    return m;
});

// bookmarked, witch uses Element.Storage or Event.cache dependent on the Prototype version
(Element.Storage ? $H(Element.Storage).values().slice(1).invoke('get', 'prototype_event_registry').compact() : 
Event.cache.values()).inject(0, function(m, p){ return m += $H(p).values().flatten().size(); });