[chaosmatic]

If you check https://blockchain.info/pools Ghash.io is back down to 39% of blocks created, which is still big, but not as scary.

A good explanation is due to the random variation in the who the block is a awarded to.

[NickSharp]

The chart you link is over the past 4 days.

In the past 24 hours, they are still at 41%.

Although I agree there's bound to be a bit of random fluctuation.

[TomGullen]

It's dropping nicely, down to 39% over last 24 hours.