'Prototype interference' can cause problems due to JavaScript distinguishing between enumerable and nonenumerable properties. It states that All properties that we create by simply assigning to them are enumerable. The standard properties in Object.prototype are all nonenumerable. If you where to use a for/in statement to find out and test what values are being used in an object would it be correct to identify enumerable/nonenumerable as saying that methods already built-in JavaScript are nonenumerable ex: toString? where assigning Object.prototype is enumerable ex Object.prototype.speak? How concerned should we be with controlling the type of property in objects by using Object.defineProperty function? Also hello from Western Canada (Calgary) :)