The reason I like reddit is because of the subreddits. There are, however, really great communities for discussing something really niche outside of reddit. Some of which have bigger communities with even better contributors than reddit.
The problem is that they are using rather primitive forum systems like phpBB and the like.
After using reddit, phpBB is like going to the stone age, imagine if hacker news was on a simple forum system like that.
I know reddit is an aggregator site, but I think they are the strongest competitor to forums, think about it: how hard is it get the gist of a discussion on one of those forums, where you have to scroll through tens of pages on a really popular topic.
my point is: why doesn't reddit create a product that will allow any site to to have their own subreddit style page completely autonomous of reddit.com?
Do they have to create a "product"? Reddit is open source, and you can download it if you like, from http://code.reddit.com/ .
You could literally build what you are describing on the Reddit platform right now.
The last I knew of it, there was a post on HN. I later asked hueypriest if their new hires would be trying to fix up redditOSS, and he said it was one of their priorities. This was a couple months ago (if not more), so it's entirely possible that they've done significant work on it. If that's the case, I suspect we'll see a blog post before too long.
I've done that, and it's not what you might call seamless. I tried to make the community its own entity, with its own look and feel. The problem is that the pages are full of links that take you back to reddit.com rather than their equivalent on your own domain. That's very confusing to non-redditors who suddenly find themselves on a seemingly unrelated site, with all the disorientation and styling-whiplash that entails.
It's a neat idea but it needs a lot more polish to be really useful.