I run one wordpress folder for a few sites (under completely different domains), which works well, apart from when installing WP-Super-Cache.
The two issues I hit were:
1. My wp-config.php file actually just imports the site-specific config file like so:
<?php include $_SERVER['DOCUMENT_ROOT'] . '../wp-config.php' ?>
So when this is added as part of the install:
define('WP_CACHE', true); //Added by WP-Cache Manager
It simply doesn't work. (It shows that at the top of the page!)
You might consider that is just due to my strange setup, however, the second is more of an issue:
2. I get this error (folder structure disguised, but hopefully makes sense):
[Thu Jul 29 23:37:31 2010] [error] [client 127.0.0.1] PHP Warning: include() [function.include]: Failed opening '/Absolute/Path/To/Site//wp-content/Absolute/Path/To/Site/wp-content/plugins/wp-super-cache/wp-cache-base.php' for inclusion (include_path='.:') in /Absolute/Path/To/Site/wp-content/plugins/wp-super-cache/wp-cache.php on line 53
That's the first use of WPCACHEHOME
If I add this line to my wp-config.php file it works fine:
define( 'WPCACHEHOME', WP_CONTENT_DIR . '/plugins/wp-super-cache/' );
So I think it must be due to the simlink to the wordpress folder?