sure, that makes sense.

i feel like you will have to have aggregate topic categories (everything about topic x) to get enough traffic in that topic. remember that there is typically a 10:1 reader:poster ratio (or more!) and that is what will get spammed.

my gut sense is that if you make topic directories for people to sign up to you are adding transaction costs to get people into the system.

i'm not at all sure what the solution is, though.

on cluedb i made it so that multiple people had to use the same tag on an item before it showed up. cluedb has approximately zero traffic, however.