There have been reports that last month there was a strong surge in spam. All types of it, referrer spam being the one web admins have to deal with. Sometimes when I check my logs theres 1000's of lines of poker sites. On my site (in my profile) every now and then, people from China shut down the site. They use programs that are meant to download the site all at once. They open so many mysql threads that my load average goes above 50. The site is non accessible then. I tried fighting it, but theres just too many ways around an .htaccess file, and too many types of site downloader clients, some of which can change thier ids. I just live with it now, they always go away after an hour or so. For this one incident I wouldnt bother changing your httpd conf file.
When the server does overload netstat -p will tell you whos all connected.