How important are "categories"?

[SmutGiant]

Say you have a site, non niche-specific, basically has a bit of everything. Say the site also has a keyword search option. How important are categories? Will most surfers not care and just search by keyword or would they go somewhere else?

What are your thoughts?

[NoWhErE]

I prefer The Hun style listings, all randomized with an idea of the niche inside the description.