For my part, I could easily do without the post-office. I think that there are very few important communications made through it.That such a statement would be made over 150 years ago, and ring as true today, leads me to believe nothing has much improved. Thoreau goes on to speak unkindly of newspapers, and news in general, equating it with nothing more substantial than idle gossip. He further proclaims the value of the great classics, urging the reader to consume them in the author's native tongue.
I cannot remember the last time anything of value was delivered to my mailbox. There are, of course, some number of bills requesting the payment of my debts. One might consider these important in some regard, though not exactly communications of value. The rest is little more than the abused remains of dead trees imploring me to part with money not yet owed on products and services I do not want. Should the United States Postal Service cease to exist today I would likely not notice its departure from this country for several weeks, if ever.
The physical postal service isn't the only conduit of wasted material and effort. E-mail is no better. The plague of spam is perhaps, in some ways to me, worse than a mountain of pulp fliers, catalogs, credit card offers, and balance transfer checks, though the environment might be worse off for the paper. The electronic post-office, lacking even the meager barrier to entry of a bulk postage charge, pushes countless bytes of meaninglessness through the Internet connections of the world. If not for the filters Gmail provides to protect me from the drivel I would hardly be able to see what might be considered of value at all. Even then the majority of my inbox is crowded with little notes, messages I will simply ignore, invitations to social events, and nothing much to be considered worthy of lasting importance. I will admit that I have, on rare occasions, been delighted by a lengthy intellectual conversation which inspired me to write further on the subject.
The ease of communication afforded by mail, electronic or otherwise, is, I believe, the very reason for its lack of value. It is easy to simply gossip, as humans are wont to do. The rapidity of creation and delivery cuts away our desire to invest effort in thoughtful communication. Of what value is a single hastily constructed sentence of dubious grammatical accuracy detailing, if one can call it such, your enjoyment of some sandwich or sporting event? How much more valuable is that paragraph and page, carefully written over an hour, which offers well thought-out insight and inspiration?
Books, then, are the prime vehicle for important communication. Books are built to last, built to carry their message into the future, convenient enough to share, and generally require a greater attention to the details of their writing. That's not to say all books are worthy of immortality, of course. But if I were to invest my time and money in procuring important communications, it would be in the medium of a book.