I recently came across an issue with this site.
I wanted a particular block created by the Views module to only show up on the Account page of the User logged in (Authenticated User). Since this block will be displaying information sensitive to the Author, it should obviously not be visible to other users. Also, since Drupal has a real issue with context sensitive information across the site in its OOTB (out of the box) configuration -- without having to load extra modules into memory, I had to hunt around for a solution that might solve a few issues.
Tuning APC (Alternative PHP Cache) to work with Drupal is a relatively painless process. As Dries Buytaert has noted, APC can help serve Drupal pages up to 4 times faster than a stock Apache and PHP setup.
However, tuning APC for use with more than one Drupal instance can be a little bit more challenging than a single site running on it's own server.
If, much like myself, you've recently activated the blog.module along with the blogapi.module, you've probably run into a problem as you navigate to the blog page of a user.