[URL]http://gigaom.com/cloud/how-facebook-keeps-100-petabytes-of-hadoop-data-online/[/URL]
Hadoop is freaking cool and is one of the most fun things I get to play with for my job. This article is pretty sweet.
I didn't deal with anything near 100PB, but greping through ~2TB of logfile data each month for interesting stuff is still pretty fun.