Savvy marketers have learned how to mount email campaigns that do a great job of reaching current customers, prospects and even former customers with pertinent information.
The overriding theme of these initiatives is that it's important to stay in touch with the people who may buy products and services at times other than when you are actively pushing for a purchase. Companies should seek any means--electronic and otherwise--to show some love to those who eventually will be called on to buy products.
Email perhaps is the natural way to do this, though there undoubtedly are others. It's a complex operation, though, since both the business and the recipient are fully aware that the ultimate goal is a sale. It's far more than sending out a form letter to everyone in the database. There is great subtlety in how to use email over the long haul.
There are many firms that specialize in these complexities, and companies should take advantage of them. Email's strengths are that it is inexpensive, relatively easy to use and reaches users individually (as opposed to a newspaper ad, for instance). However, it's equally easy to misuse. This leads to annoyed recipients, not the best recipe for sales.