A reader writes:
I don't think the correct parallel is broadcasting. It'd be the kind of letter-writing that serious writers did before the telephone came into everyday use. Writers of stature (like other educated people) routinely spent hours every morning writing the letters that now get collected, edited, and published. Why should blogging contaminate your other work more than such masses of letters did? They don't seem to have detracted from the more sustained work of Johnson, Carlyle, Austen, G. Eliot, Wolfe, C.S. Lewis, or Waugh - not to mention all those epistle-flinging Frenchmen and -women.
The difference is that the flung epistles were private and not intended for instant mass dissemination. That alters writing into more of a live-performance, with all the snafus and inconsistencies and occasional small glories of the same.