I could almost taste the web app building concept when I was putting together a test/planning site for a Wii Community last year (they ended up settling elsewhere, but promised to look at wikidot again when they outgrew that site).
There's a lot you can do with listpages and templates, but I lacked meaningful user grouping, event scheduling, more diverse permissions, and form-based interaction, among other things I couldn't quite put my finger on. That experiment was the source of a lot of my wishlist requests.
Wiki-based foruming also gets a thumbs up from me, so long as it comes with site-specific settings and increases power and customizations when it comes to avatars and signatures. Hopefully, you'll also move "signature" ability from a user-by-user setting to a site-by-site setting, b/c while an admin might pay to make sure his users can have the bells and whistles, a lot of ordinary users wouldn't want to pay for such a tiny thing, but they also wouldn't want to use a forum that didn't provide such a basic amenity. Combine wiki foruming with web apps, and wikidot could do for forums when they are doing for blogs.
I wish wikidot luck on this. There are a lot of useful social networking applications coming together—for instance there was a site for readers that launched recently that allowed you to build your online library, befriend readers of similar books and share recommendations. I bet you there were tons of readers who had a similar idea long before that site launched, but they didn't have the programming expertise to be able to build it. A web-app builder wikidot could become the go-to site for all manner of niche functionalities thought up by people who don't want to devote their lives to programming.