I agree the web-of-trust model is a good idea for the future. Lobsters has something sort of like it in that you can see a tree of who invited who. I don't think it has a fully fleshed-out system for reputation flow on that basis though.

I don't think the old web was really a walled garden, though. It was just a sort of isolated garden that was harder to get to. There was nothing outside it threatening it. Now the garden needs walls because there are a lot of dangerous things outside.