Let us sign up for real accounts would you? This demo account is pretty restrictive. You can put a cap on the number of accounts allowed to be created if you're worried about scale.

On the "Manage Links" page, what do "Run", "Clone", and "Pause" do?

You're right about the UI needing some work, but it's good that you're focusing on getting a prototype working quickly. Now iterate.

You're going to need a big community before someone can waltz in and say "I'm interested in gardening videos about pruning roses, any recommendations?". I'd suggest narrowing your focus to be a tech site similar to how Digg and Reddit started out. That way you'll actually have an audience that can answer requests from one another during the early days. Then later, if you want to broaden your focus, you can become more general. There are a million ways to fuck this up (case in point: Digg), so do it carefully.