i suppose it would rather be called an instance of an anonymous class, as an anonymous object i think is already used as an expression for the parameter passed (not in the signature but in the calling routine) in the following example :

Function anyFunction(AnyClass I_oAnyObject) { }

{
[...]
anyFunction(new AnyClass());
[...]

}

Take this example from the ext library for example:

/*
* Ext JS Library 2.2
* Copyright(c) 2006-2008, Ext JS, LLC.
* licensing@extjs.com
*
* http://extjs.com/license
*/

Ext.onReady(function() {

var patients = [{
insuranceCode: '11111',
name: 'Fred Bloggs',
address: 'Main Street',
telephone: '555 1234 123'
}, {
insuranceCode: '22222',
name: 'Fred West',
address: 'Cromwell Street',
telephone: '616 555 222'
}, {
insuranceCode: '33333',
name: 'Fred Mercury',
address: 'Over The Rainbow',
telephone: '555 321 0987'
}, {
insuranceCode: '44444',
name: 'Fred Forsyth',
address: 'Blimp Street',
telephone: '555 111 2222'
}, {
insuranceCode: '55555',
name: 'Fred Douglass',
address: 'Talbot County, Maryland',
telephone: 'N/A'
}];

For example, in script.aculo.us, when you want something to fade from one color to another, you do something like Effect.Fade(“my_dom_id”, { from: “#000000″, to: “#ff0000″ });

(I don’t remember the exact syntax, but the idea is there )