Unlocked, partially because I think I understand the question and partially because I know everyone else will be able to too.
The way I understand it, what's being asked is: can an entire DSi site be comprised of just a chatroom?
What's really at the heart of your question is on what makes a good DSi website. And understanding that is marginally unique from what makes a good website in general. In my opinion, it's branches from the purpose. Some sites are designed to be bare-bones for ease, others to have variety for enjoyment. For example, the fact that DSiPaint has a bunch of apps is what makes it popular--there's a lot to do here; now a site like DSiCade, which although it has games, revolves around its famed Shoutbox chat. It is undeniable that both sites are popular. Does that say something?