someone couldn’t keep it in it's pants so we could have got negative diff
I tried calling my buddies at KNC, and asked them to turn off their gear for a few days so that I could win with my small negative guess. They just laughed at me......
On a more serious note, I think this is more than just "variance". The last two increases together suggest that we have a real and sustained increase in hashrate. Absent some kind of disaster, or collapse in BTC price, we won't see a difficulty below 50 Billion again (IMHO).