Tags or categories for a general forum?

Question

Design

What do you think is more suitable for a forum dedicated to different topics?
1. Categories on the main page. In each category - thematic discussions.
2. On the main page - all discussions. Each discussion is assigned tags. There is a tag cloud with built-in search to find discussions with a given tag.

Answer 1

Take a look at www.quora.com , for example .

Answer 2

I think it's both. =)