There's been a lot of talk lately about RSS replacing email...and the spam problem is what most people have been pointing to to justify their position. Hmm.
I think having RSS feeds in the NewsGator forums actually gets us pretty far down this path. The Lockergnome forums do this too, and I'm sure there are others. Suppose someone posts a question about NewsGator in one of our forums. I (and many other folks) get this notication via RSS. I respond to the question in the forum, which causes the original author to get a RSS notification of the change. And so on, until the thread is complete.
Really, I think this is as close to a one-to-one conversation as we've gotten with RSS. The forums provide the infrastructure for these conversations, so people can easily post; and they also provide an archive of everything that's been said. The big difference between this and email is that here, the world is watching the conversation.
To get a bit closer, we could probably have "private" threads where the participants are the only ones who can see them, and the forum RSS feed would be customized for each subscriber, depending on which threads they had acess to. This really isn't necessary in our particular case, but it's something to think about.
All that said, I really don't see RSS "replacing" email, as some have predicted...they both are great communication mechanisms, and I believe they solve different problems. Email is great for one-to-one or small groups of people who know each other, and RSS is excellent as a broadcast mechanism.