And how are you certain that they will not be able to protect the blockchain?
When figuring out what a currency is worth, the security of the blockchains should be considered. if the blockchain cannot be sufficiently distributed, the risk of transaction reversals or intentional forks should destroy any value in that coin. Because of this vulnerability most coins are overvalued.
nice point, but just
a question about bitcoin: ok the total hash power is immense but a pool has >%40 hashpower alone and just two pools together suffice to exceed 50%, how about that?
the issue of the btc blockchain has been discussed exhaustively on btctalk, and there are many threads discussing your scenario. take a look also at the "weaknesses" section in bitcoin: https://en.bitcoin.it/wiki/Weaknesses
if two pools combine to exceed 50% of network hashrate this is problematic, but likely this is also accidental. this has happened to many coins before, and because it's unintentional, we can come to an agreement to correct the forked chain. there is a difference between an accidental 51% scenario, and a malicious one.
It would be almost impossible to maliciously attack the bitcoin blockchain, as the bitcoin network hashrate is 28,400,000 Ghash.
https://blockchain.info/charts/hash-rateIn contrast, auroracoin has only 11ghash protecting it. it would be quite easy for a single user or company to attack and fork auroracoin. there are many users on this forum with more than 11Ghash working right now e.g.: https://bitcointalk.org/index.php?topic=7216.msg547977#msg547977
i'm not saying any of these users are malicious, but it's entirely possible for a single person to possess enough hash power to damage auroracoin. compared to auroracoin blockchain, bitcoin is near impossible to attack in this fashion.
11ghash is not that many video cards.
Almost no coin's blockchain is really secure.
This is exactly the point i was making earlier: most coins are insecure. due to the insecurity, most coins are overvalued. This point of vulnerability is almost never talked about in the altcoin forum, but it is a huge issue.
if i can't lock my house, then i wouldn't leave anything valuable in there. Similarly, i wouldn't put much value into a coin i could not secure.