Extending Object.prototype JavaScript

I am not asking if this is okay:

Object.prototype.method = function(){};

This is deemed evil by pretty much everyone, considering it messes up for(var i in obj).

The Real Question

Ignoring

• Incompetent browsers(browsers that don't support Object.defineProperty)
• Potential for property collision or overriding

Assuming you have some incredibly useful method, is this considered wrong/unethical?

Object.defineProperty(Object.prototype, 'methodOnSteriods',{
  value: function(){ /* Makes breakfast, solves world peace, takes out trash */ },
  writable: true,
  configurable: true,
  enumerable: false
});

If you believe the above is unethical, why would they even implement the feature in the first place?