I much prefer a good conspiracy theory. Does certainly feel like the big boys toying with the diff.

Or perhaps someone bought a load of these 100ghs stick miners:

http://aryadutaminer.com/cheap-the-bh-miner-usb-bitcoin-100ghs-sha26-miner-and-free-shipping.html

seriously that site looks so dodgy

while hashingit.com is brill.