High CPU usage
I am using the WordPress plug-in in WordPress multisite. My hosting company said that I am using too much CPU time and suggested that I install P3-profiler. After I ran P3-profiler, I found that the AddThis plug-in is the biggest abuser.
Recently, the webmaster of BlogLines.co.za told me to use something else instead of AddThis because he said that AddThis uses too much of the CPU. I didn't do anything about it and did a lot of other optimization because I like AddThis. You can read about the various optimization methods I used at: http://www.top10googleresults.com/keep-hosting-fees-down-decrease-cpu-usage-speed-up-your-website/
However, after all the other optimization it's still not enough and I'm left with having to remove AddThis from multisite and my many other WordPress sites. I also found other people complaining about the same problem. I wish you could find a way to eliminate this problem.