Community response to:

  http://www.quora.com/Is-Bitcoin-doomed-to-fail

Is Bitcoin doomed to fail?

> 1.) Technical
> it would require ~2k CPUs for 1h to steal 5M BTC.

Let's do the math.
 - Amazon Quadruple Extra Large Cluster Compute Instance $2.10 per hour. http://aws.amazon.com/ec2/pricing/ 
 - That instance is 2 NVIDIA M2050s, or about 32 Mhash/s per https://www.bitcoin.org/smf/index.php?topic=1334.msg26185#msg26185 

The current network is about 150 Ghash/s.  To get 50% of current network hashing, that means you'ld need to match that amount.
That's 4,688 of those XL Cluster instances.  Hey ... that's just under $10,000 for the hour.

it is unlikely that there is that amount of capacity available to just spin up on demand, however.  And having just 49.9% of the hashing strength won't be enough.

So if you take over the network, what does that let you do?

Yes, there are over 5 million bitcoins that exist, but they aren't yours to spend.  You can try to accumulate bitcoins and then double spend once you have control of the network.  Assuming you start sending those to Mt. Gox and other exchanges in hopes of double spending, its quite likely the combination of a ramp in the number of nodes plus an influx of bitcoin funding by the exchanges wouldn't go unnoticed.

Amazon is likely to be the only one to profit from such an attempt.

[ ** Is Bitcoin's strength against an attack at this phase that you cannot quickly spend any amount of significance? **]

> 2.) Legal
> BTC will represent a deadly threat for a national state, and that they would react accordingly using their full moral, legal, judiciary, police, military, PR, press powers to shut down such a threat.

Governments could make trade using bitcoins difficult, that is true.  If they make it a crime to trade with bitcoins then only criminals will trade bitcoins, or something to that effect is how the saying goes.

> 3) Competition
> the lock-in power of such network is extremely low, and the entry barrier for competitors is also very low

There already is competition.  Testnet Bitcoin is a live, functioning parallel currency.  Today you can mine for it, exchange it .. it even trades on Bitcoin-OTC!  But you might want to think twice before putting real money into it.  Because Testnet BTC is not protected by 150 Ghash/s like Bitcoin currency is, it is rather vulnerable at this stage.  

There will be competition to Bitcoin at some point, certainly.

> 4) Community
> infiltrate the community of developers in order to push their own agendas

Bitcoin is open source and runs on open protocols.  Let the best fork win.