Many administrators disable apache symlinks for security and performance reasons.
For performance purposes, please view this page on apache tuning: http://httpd.apache.org/docs/2.2/misc/perf-tuning.html
Wherever in your URL-space you do not have an Options FollowSymLinks, or you
do have an Options SymLinksIfOwnerMatch Apache will have to issue extra system calls to
check up on symlinks. One extra call per filename component. For example, if you had:
<Directory />
DocumentRoot /www/htdocs
Options SymLinksIfOwnerMatch
</Directory>
and a request is made for the URI /index.html. Then Apache will perform lstat(2) on
/www, /www/htdocs, and /www/htdocs/index.html. The results of these lstats are never
cached, so they will occur on every single request.
You can see how symlinks can be an exponential performance problem depending on your environment and code.