Have you ever had one of your sites get hacked?
modoc: Yes.  Many years ago a server was gotten into by a brute force ssh script.  The cracker then used a local exploit to gain root access and run all sorts of unpleasant software, downloaded my databases, etc...I ended up just getting a new server, as I couldn't track down all the things he'd done.  I started learning about server security.  I reduced the number of people who had ssh accounts, and installed stronger password rules.  I use iptables to block brute force SSH attempts.  I use logcheck, chkrootkit, and other tools to constantly monitor my server.