Twitter is on the face of it such a simple application that it can be built in 40 minutes in Grails.
For a consummate software engineer with state of the art tools, building a twitter in clone 40 minutes that can scale... might even be easy today given a proper set of cloud enabled tools. But, even if it is an exact working copy of twitter and can scale to ten times the size of the current twitter... it's NOT twitter and will never be twitter.
Twitter is a brand now. It is more than merely a functional set of software performing a simple function. It is a user experience driven not by technology but by human interaction. That experience in itself constitues a wholly separate kind of real engineering.
In fact, if Twitter were to completely rewrite their application in a whole new technology stack, the net effect (providing only nominal interruption of services) would probably be zero on their brand. That's because aside from being a brand and an application Twitter is about doing something very simple (and rather boring to systems level folks) with your computer and with existing internet technologies.
So why aren't there a bajillion Twitter-like applications? Lord knows at one point people tried. Well there are, just none of them are mentioned on CNN and the Colbert Report. There was a time when Twitter was novel and now it's not. But, that doesn't matter anymore because we all know about Twitter.
It's just like Windows. Or Google. Or Kleenex. And all the interesting socio-economic issues that go with the success of a brand like Kleenex and the problems Kleenex has keeping people off its damn lawn. See, you can't call your tissue paper Kleenex because only we can call it that even if what you make basically is in fact the same thing.
You may not care if a tissue paper is of equal quality to Kleenex. You may choose to still buy Kleenex because you remember warm and fuzzy things about that Kleenex box. You know what to expect from a Kleenex box. You like Kleenex. So you buy it.
Whenever you consume something with an intent beyond the mere act of consumption then anything that distracts you from your end goal is a waste of attention. In this day and age we can't afford to pay much attention so we had better conserve it. Your customer service representative is there to try and keep you happy and consuming.
The same is true for technologists just as it is for any other demographic. When a technologist becomes comfortable with his favorite tool X no other tool can be as good as X even if it is better. That's because technologists get brand loyalty viruses too.
So I'm going to ask you... are you sure you like to use the tools in your toolbox because they are the best for the job or are you just buying Kleenex because that's what you buy? Is it worth thinking about?