Dean Edwards: Callbacks vs Events
http://deanedwards.me.uk/weblog/2009/03/callbacks-vs-events/

Callbacks vs Events

カスタムイベントを取り扱う際のコールバックシステムの問題点と解決策

Most of the major JavaScript libraries claim to support custom events in one form or another. For example, jQuery, YUI and Dojo all support a custom “document ready” event. However, the implementation of these custom events is always some form of callback system.