Recently a mostly annoying occurrence was filling up my log files with errors. The problem seems to be with some atom news readers. The standard atom feed for this site would get turned into a request that would be "/atom/atom/atom/atom".... and so on. Often longer than Apache knew what to do with it.
So, a single line added to the httpd.conf file solves the problem.
RewriteRule ^(.*)atom/atom(.*)$ - [G,L]
Now the request is met with a 410 error - resource gone. With a little luck this will lead the coders of the errant software to start picking up on the problem.