You can view Simon's 2009 Ted Talk, one of the 20 most-watched TED Talks as of 2012:
Assume by now you had bought into the concept of "why" is more important than "how" and "what" in terms of actions, so why do I want to adopt newsletter marketing?
Why Newsletter Marketing
These are the why's of mine:
Why bother doing newsletter? Because it is much cheaper to retain existing customers or visitors and close the sale than acquiring new customers or visitors from scratch and close the sale. Customer retention is often overlooked. I had made this kind of mistake of not implementing any maintaining ongoing connections with contacts as simple as newsletter marketing before. To grow the business more organically, form a good relationship with prospects is no doubt the key.
Customer/Visitor acquisition cost is never cheap. Therefore, for every acquired customer (or visitor) failed to be retained over time, you have to spend the same amount or more of marketing dollar for acquisition to bring prospects back. If you already acquire the visitors, it is cheaper to engage with them to keep your brand in front of prospects to close the deal. The newsletter is a great marketing tool for this. Your quality mailing list is like a repository of achievement you've done for your business. It is like the predictable income of future. You won't have sale right away, but sale will come eventually when prospects are ready. If you don't even have such repository where you'll be reaping the benefit from in the future, your business is not predictable and is not likely to be growing.
What to Cover in the Newsletter