Email is one of the most valuable tools there is for building Web site traffic.
If you spam, you will go instantly to Hell. Or at the very least, you'll waste time and money to hurt your traffic rather than help it. Spam is for MLM mountebanks, purveyors of porn, weight-loss wannabes and just plain crooks. Email lists, however, are quite legitimate, and are often terrific traffic-builders. An announcement newsletter, which allows you to send email to visitors who sign up for the list, can be used to notify customers and potential customers of new features on your site, special offers, etc.