What am I looking for?

I need a little help narrowing down what I am looking for.

It's kind of a cross between a blog, a directory, social networking, and a kind of blog network. Wordpress MU and mediawiki come close to what I am looking for but I would like the ability to catalog for easy search.

What I am looking to do is this-- create a directory for like minded niches.

For example, let's say I want to create a directory only for personal fitness trainers. The idea would be that I would register a domain such as personaltrainerdirectory dot com or something similar.

A personal trainer could create there own page to advertise what they do, their location, etc.. But it would be more than a typical directory program allows, they could write and add pictures just like a blog. They would share the domain name and receive their own folder. personaltrainerdirectory.com/joesmith

The domain and website would hopefully increase rapidly with new free additions. I would simply hardcode a google adsense ad in the top somewhere leaving their pages available to have 2 more of their own adsense or whatever they want.

I'm pretty sure I could do this with Wordpress MU, but I'm concerned it might be overkill or overly complex for the average non blogger who just wants a single page. Also, I'm concerned that the site would suffer without any real search capability if someone wanted to browse by city, state, etc.. unless there is some plugin for wordpress.

What comes to mind is creating something like milliondollar wiki but I don't think mediawiki software is designed so an individual page could have it's own theme or whatnot.

Any advice or ideas?