From release notes for FC5T3 (web)

[Bruno Wolff III]

On Tue, Mar 07, 2006 at 21:10:12 +0530,
  Rahul Sundaram <sundaram at fedoraproject.org> wrote:
> Just having a  program with a security hole on disk through a 
> "everything" installation that you dont use is a potential problem that 
> leaves room for an exploit. Basically dont install stuff that you wont 
> use and audit everything that you install and use carefully. SELinux 
> does go a long way towards preventing many of these issues but the 
> default targeted policy in Fedora doesnt restrict all the programs 
> unlike the alternative strict policy which might require a good amount 
> of customization for regular use.

And just walking around outside risks getting struck by a lightning bolt.

The risk of installing most categories of software and then not using it is
negligible.

The main risk is in installing software that gets used without your knowing it.
While direct services are not enabled by default, apache modules and plugins
for browsers and email clients can cause unexpected problems.

However the vast majority of the packages on Fedora don't fall into those
categories. And security is not a reasonable excuse for not making it easy
to install them.