A large focus of my redesign was improving site speed, and in doing so, I took a look at my site's error_log for the first time in a long time.  I was shocked when I found out that 90% of my site errors were either hacking attempts or hot-linked files from hundreds of different tumblr.com subdomains.  Thousands upon thousands of PHP fatal errors due to lack of memory saw me seeing red pretty quick -- no wonder I was having periodical speed issues!