no single entity has 51% of the hashing power .. nobody has even 30% of the hashing power of bitcoin so what you are arguing is theoretical.
sure someone could buy 51% percent of the hashing power but it would cost them several hundreds of millions of dollars and as I said it would only be temporary because the difficulty rises exponentially.
even if someone has 51% of the hashing power for an extended period of time.. they cannot control 51% of the coins..
someone quite easily managed to steal 30% of vericoin through very little effort at all .. all they needed to do was buy, borrow or steal 21% more and they would have been in a monopoly position for the production of vericoins for as long as they held onto their coins. they would not need an air conditioned facility, they would not need to keep upgrading their hashing power to stay on top, they would not need to keep paying massive electricity bills. They would only need to run 1 computer and they would be able to produce 51% of all new coins for eternity (if they so wished)
now if someone managed to steal 30% of all bitcoins in existance or even 20% that would be a very huge problem for the bitcoin economy... but someone having 51% hashing power and being able to produce 25 BTC every 10 minutes... that's not really comparable not even in the same ball park.
people who compare 51% PoW with 51% PoS attacks really do not understand the complete difference in scale of how much power each attacker has.
being king for a day is nothing compared to being king forever.
(well at least until the coin gods hard fork you off your throne.. LOLZ)
1. we had ghash.io several times with over 51% hashpower, this is fact.
2. if someone has 51+% of the hashpower they control the network, because they can alter the blockchain after their will
3. yes someone stole 30% of all vericoin, what do you think would happen if someone manages to hack ghash.io? and maybe some other big pools on top of that.
4. the attacker would need to pay nothing if hes hacking big pools and gets control over them, initiate a double spend attack and give him millions of bitcoins for free - all that with just one computer.
5. of course there are differences between pos/pow, im not denying but if you look on a bigger scale its not much difference at all
/edit
As a general rule, just about everyone around here has some skin in the game when it comes to Bitcoin. Since the sudden theft of 4 million Bitcoin would almost surely be a lethal blow to Bitcoin (and quite possibly to the very principles of cryptocurrency at the same time), I would love to see what song the people around here sing in the face of such an event.
I bet it would be vastly different for quite a few people in this thread.
if I recall correctly Mt Gox alone lost about 7% of all bitcoins to hacks.
so greater than 4% has already happened and bitcoin is not dead.
regardless of PoW or PoS... if a single entity had manged to steal 30% of bitcoins there's no doubt in my mind that it would have shaking bitcoin to the core also.
I'm not arguing that PoS is the problem only that PoS combined with small coin size encourages centralization and centralization is the problem.
4 million bitcoins are not 4% ^^"