filesystem

I'm new to the media module, and am trying to extend it to pull a list of images from the file system rather than the database.

Here's my situation:
Imagine a multi-site environment like drupalgardens.com where you may have dozens of unique websites using a shared code base. You'd like to provide a shared image library for all website owners to view and choose images from. For obvious reasons, you don't want to maintain this library at the database level for each site, but rather at the code level just once.

I recently (yesterday) got my hands dirty with a huge news-site in Greece that suffers from really bad performance!

I checked the filesystem and saw that the previous admins placed all files under the "sites/default/files" folder, without creating subdirectories. Now there are more than 20000 files under there, increasing by 100 per day.

Could this be the source of all evil? The owners of the site say that the problems are getting worse every month so I imagined that by re-arranging files in the file-system I would gain something in performance.

My situation is:

I have a website example.com, i want to mirror this site completely except for the theme so that in apache i can direct mobile devices to m.example.com where they can use exactly the same site but with a mobile optimised theme.

I know there are numerous mobile modules out there but they suffer from caching limitations, ie, when a page is accessed from a computer, that same cached page is sent to any subsequent requests, including mobiles.

I know there are also domain/subdomain modules out there also but they are overweight for what i need.

File attachments seem to be broken. I'm trying to attach a file to this post (replacing the file that's already there), but the "File attachments" fieldset says "File attachments are disabled. The file directories have not been properly configured. Please contact the site administrator." I just checked, and I'm seeing the same thing on this post.