Et af de vigtigste argumenter blandt tilhængere af den virtuelle valuta Bitcoin er, at den er decentraliseret og derfor ikke kan styres af nogen. Dette holder dog ikke helt stik, da man med en produktion af 51 % eller mere af den totale Bitcoin produktion, opnår en teoretisk kontrol over valutaen.
En sammenslutning af Bitcoin-producenter kaldet GHash, har af flere omgange rundet de 51 %, senest i en periode på 12 timer.
Ittay Eyal fra Cornell Department of Computer Science beskriver problemet som følgende.
Ittay Eyal skrev:
A 51 percenter can control which Bitcoin transactions happen. It becomes a monopoly. It can set arbitrarily high transaction fees, for example, or even extort someone to allow them to perform transactions. It could block or delay all transactions but its own. One of Bitcoin’s goals was to be a free system, independent of anyone’s control. With small pools, no one has this kind of control. With a 51 percenter, there is.
GHash er godt klar over problematikken, men insisterer de aldrig vil misbruge den magt det giver, eftersom det ville ramme dem selv meget hårdt.
Ghash skrev:
GHash.IO does not have any intentions to execute a 51% attack, as it will do serious damage to the Bitcoin community, of which we are part of. On the contrary, our plans are to expand the bitcoin community as well as utilise the hashing power to develop a greater bitcoin economic structure. If something happened to Bitcoin as a whole it could risk our investments in physical hardware, damage those who love Bitcoin and we see no benefit from having 51% stake in mining.
Trods løfterne er der mange, som er bekymrede over, at et af de fundamentale grundlag bag Bitcoin risikerer at forsvinde, ved at en enkelt gruppe nu kan styre den virtuelle valuta, uanset om de vil eller ej. Håbet er derfor, at GHash gennemfører tiltag, der reducerer deres andel af producerede Bitcoins.