Having that experience right now with my programming e-mail newsletters. Just ticked over to 50,000 subscribers today. It started as a side project and I got more than enough "e-mail is dead", "where's the RSS!?" and "it's been done" at the start :-)
That's awesome .. I just subscribed to your podcasts from podcasts post on the frontpage[http://news.ycombinator.com/item?id=3580367]. Which newsletter exactly are you talking about?