I've read over and over again how people think Slush is up to something or planning something or intentionally doing something so people won't make as much. If you honestly believe that, why do you stick around?
I wonder that as well. The hash rate dropped probably because people were antsy about the whole 2 blocks in 27 hours thing and moved on to different pools. Everyone always feels like something nefarious is going on, when they are more than welcome to choose a different pool to be a part of.