new .net site - best url name structure?

[confused]

Hello everyone... long time lurker... first time poster... please go easy on me.

Doing a new classifieds ad type site with .net. Using the asp.net url rewrite module. My question has to do with the actual structure of the file names but the following may help understand why I am "confused".

At the San Jose SES, MSN, Y, and Ask all stated that they like "flat" file structure of sites vs. a deep structure. They all indicated should be no more than two directories deep. It was also stated to try and limit "-"'s to no more than two. This seems to be true since Allegra, that they do not want to see too many "-" or "_" or sub-domains. Especially, if you look at highly competitve keywords like "real estate" which have alot of "locations" this seems to be the case as most SERPS are showing only top level domains or 1 page deep with little or no "-" or "_".

So... what that said, this new site has alot of locations for the classified ads. What type or URL / file structure would you suggest?

A) widgets.com/catagory-id-city-state-zip.aspx
B) widgets.com/catagory_id_city_state_zip.aspx
C) widgets.com/catagory/state/city/zip/id.aspx

or any other's that I'm not smart enough to figure out?

A & B - are "flat" should rank better but look ugly and may raise flags due to number of - and _ 's... "especially in the future"

C - looks nice, user friendly... possibly not as "optimized" for SE's and very deep structure which may turn off SE's (may not be an issue in the future?)

My concern is to roll out the site get 30K pages indexed, then change the sturcture and have all of those "301", 404's and lost of PR.

Any comments and suggestions the will help us build a great long-term webiste would be greatly appreciated!

[randfish]

When they said 'flat navigation' or structure, I find it difficult to believe they meant the number of /directories/ in your URL. I'm pretty sure they just mean - keep the path to a target page as short as possible. How? Make it require the fewest possible clicks to reach any page on your site - it's not just SEO; in my opinion, it's a good usability practice.

[confused]

Hello randfish... o.k., I think I understand what you are saying and maybe I was confused about what they said at the SES. It makes sense that they are talking about number of clicks to a page vs. depth of file structure.

If that is in fact the case, do you feel that the A B or C would be the best structure for the long haul and what would you be the maximum number of "-" or "_" 's you would use?

I reviewing recent serps it seems that it's most "_" or simply TLD's?

[dazzlindonna]

How about a combination/compromise?

widgets.com/category/state-city-zip/id.aspx

Fewer directories deep, and fewer dashes.

I agree though that they were likely talking about link levels, but if you just want to be on the safe side, maybe some combination like the above would make sense.