Commuting - Commuter bike project

Hi all, I've been wanting to build myself a commuter bike but I have a few questions before i start on it.

I'm planning on purchasing a Novara Buzz Frame from a guy locally. yeah i know it might be cheaper and less of a hassle if i just bought the whole bike but i enjoy building it up by myself. Also, i want to build my bike close to this one i saw on CL, http://sfbay.craigslist.org/eby/bik/3113065758.html

Here are my questions;
1- are the wheel hubs road bike hubs or MTB hubs? any size issues will i come across with regarding with the hubs?
2- Why do most urban bikes come with MTB components instead of road bike components?
3- ... I wish i had more questions but my mind is drawing a blank. lol. if i can think of anything ill ask more. LoL

any help would be greatly appreciated.
Joel

1. front hubs - no real difference. rear hubs - MTB have 135mm O.L.D; road are 130mm - see Sheldon Brown's site for definitions.

2. cost; MTB parts are made in much higher volume, resulting in lower cost.

3. check out: http://forums.bicycletutor.com/

I like the CL bike! If its legit that looks like a deal!

thanks for the input.

another question, trying to look for specs on some of the bikes with disc brakes but i cant tell if they are using mountain bike hubs or road bike hubs. do they make road bike hubs that's disc brake ready or is it just mtb hubs?

MTB hubs for discs