Spike in november 2012 looks strange for me, but it exists in data.
Nice Graph! Found this on the website about the spike
11/17/2012Difficulty is back to 'normal'
The last jump of difficulty value (from ~100k to 385513) was quite unexpected. But it's back what is even more surprising! Important note: no double-spend or forking attack were mentioned.Some numbers were also inserted in the blocks; looks like a counter. Btw retargeting algo works out perfectly. We are ready for the next "wave".
Anyone luck on mining?