[…] the brevity, improvisation and in-the-moment quality of e-mails and texts are those grand old defining qualities of spoken language. Keyboard technology, allowing us to produce and receive written communication with unprecedented speed, allows something hitherto unknown to humanity: written conversation. In this sense, they are not “writing” in the sense we are accustomed to. They are fingered speech.
A sense that e-mail and texting are “poor writing” is analogous, then, to one that the Rolling Stones produce “bad music” because they don’t use violas. Note that one cannot speak capital letters or punctuation. If we accept e-mail and texting as a new way of talking, then their casualness with matters of case and commas is not only expected but unexceptionable.