From release notes for FC5T3 (web)

[Bruno Wolff III]

On Tue, Mar 07, 2006 at 17:43:55 +0000,
  Andy Green <andy at warmcat.com> wrote:
> Les Mikesell wrote:
> 
> However you just have to read the security lists to see that your
> chances of having apps with security flaws on your box goes up linearly
> with the amount of code you have installed.  It would be the same (or
> worse) in the MSFT world with the added spice that every install might
> bring spyware.  You could literally 'weigh' the code on your box and
> estimate the probability of getting dinged with a security problem in
> the next year, and that probability goes up the more apps you have.

But the chances of having an actual security problem does not scale linearly
with the software installed. Code that isn't used is not generally a problem
(though there are some categories where just having it installed can be
a significant risk).