My good friend Michael Goodman and I have been having a discussion about email newsletters vs email RSS feeds.
If you've been to my website, You notice that I have a newsletter. And if you look at the sidebar of this blog, you'll notice that you can sign up to receive the RSS feed of this blog via email. In other words, I have implemented both.
You would think that the email RSS feed would make the newsletter superfluous, and I predict that in the not-to-distant future the classic email newsletter will be dead. For now, however, more people sign up for the newsletter than the email'ed RSS feed.