Now imagine monkey patching in a programming language with true multiple class implementation inheritance and dynamic multiple argument method dispatch… Common Lisp was fun!
Cool - I decided to write a String.Right() extension method just last week: http://harriyott.com/2008/07/extension-methods-in-c-again.aspx
Several years ago (v. 1.4, I think) Prototype added some methods to Object.prototype at which point users rebelled and the author, Sam Stephenson, rightly removed it.
Um if you are talking about the extensions to Array, then yes there was a (mini)rebellion by some. But they were not taken out as they only broke badly written code which did not follow standards. See Associative Arrays considered harmful by Andrew Dupont for more info.