Letter-writing

I had a thought the other day... I wonder if the demise of correspondence via letters has resulted in a reduction in significant thought. Here's the idea: When long-form letter writing was the predominant means of long-distance communication, you had some astounding exchanges (Descartes' correspondence with pretty much everyone, for instance). Many great thinkers first detailed their theories in these long letters, and I wonder if the form itself made that more likely. Think about it - when you're corresponding via letter, longer messages are more efficient (whereas the opposite is true today, with email, IM, and tweets). Longer messages mean more time writing, and more time writing means more time thinking through what you want to say. As a result, then, writing long letters may have helped people think through their ideas more fully before making them public. If that's the case, then it very well might be the case that today's preponderance of short-form communication makes it much less likely that anyone will release a complex idea fully-formed – but the greater frequency (and reach) of their interactions with other people may overcome that deficit. Could it be that letter-writing was waterfall, and email, IM, and Twitter are agile? (And might this post play into that precise analogy, being far from presenting a fully-formed theory itself?)