Nobody knows who owns ghash.io, but it seems like there is 1 or more privat persons behind it.
Given the fact that every day 3500 Bitcoins are being mined and ghash.io doing about 25% of it http://blockchain.info/pools it means they earn every day 875 Bitcoins, thats 315.000 a year, given the fact that we have the same amount of Bitcoins being produced the next 3 years, this person(s) will own more then 1 million Bitcoins in 3 years.

I even read on this forum that ghash.io tried even to manipulate a bitcoin casino with not confirmed but sent bitcoins.
Thats something which should scare the Bitcoin community. At least it seems like not so difficult to own a hugh percentage of mining power, when a government or an organisation like the NSA starts to do their own mining pools, they could easily have more then 50% even. I think thats a question of time when it will