I'd just like to throw in my vote for web-based forums. I, at least, vastly prefer them, because for me, they are simpler for me to use and understand. Any computer I'm on is going to have a web browser and if it has a web browser I can check out the forum in perfect happiness. I don't have to carry around an email client, I don't have to learn some bizarre email client interface to get all of the features I want, such as message notification, threading, archival and so forth. All of that just *works*. So for me, webforums are a big win in the simplicity department.

I suppose you could argue that they are lacking features compared to a really good mail client, but that would require a much higher learning curve and I never really use, or want, any of those features. If I want to compose messages in a better editor than this text box I can just copy and paste from a real editor.