WordPress MU

I'm wondering if it's better for SEO to have subdomains or folder categories, like this:

sanfrancisco.myblog.com/2009/04/02/title-of-post
http://www.myblog.com/sanfrancisco/2009/04/02/title-of-post

Or, would it be better to remove the category altogether and have all posts under the root level: http://www.myblog.com/2009/04/02/title-of-post

What's best practice and what's best for SEO?

/category/title/

And good content.

Also, good aggregation of sub-blogs onto the main blog is key to getting the googlebot to crawl the sub-blogs, regardless of subdomain or subdirectory installs.

Subdirectory mode should add to your overall domain's pagerank but at an individual page pagerank level, the two URL approaches should be about even.

Andrea, is there any reason why you'd go with /category/title/ rather than just /title/ ?

For possible category/post title conflicts.

If an article is always in a /year/month/day/title format, would that fully mitigate the issue?

Yes, but it wouldn't be "better" SEO. :)

You can do just /postname/. I'm only mentioning possibly category name conflicts so you know ahead of time.

/postname/ is okay, but for a blog with a crapload of posts, it's very nice to have the date in the URL... because it does help me to have it be human readable... and it helps for tracking/filtering in analytics software.

I don't know if Google/other care about the date in the URL, but it seems to me that it would make it a lot easier for them to determine relevancy based on date posted.

Google doesn't seem to care about the URLs... I'm running subdirectories with long urls and global tag clouds and google quite happily wanders all over my posts (if my apache access log is anything to go by)

Steve, it's not a question of google crawling. It's the pagerank it gives to what it crawls. Finding the search terms in the URL is just one thing that boosts the pagerank score.