SHA-256 and ECDSA which are used in Bitcoin are well-known industry standard algorithms. SHA-256 is endorsed and used by the US Government and is standardized (FIPS180-3 Secure Hash Standard). If you believe that these algorithms are untrustworthy then you should not trust Bitcoin, credit card transactions or any type of electronic bank transfer. Bitcoin has a sound basis in well understood cryptography.

Early adopters are rewarded for taking the higher risk with their time and money. The capital invested in bitcoin at each stage of its life invigorated the community and helped the currency to reach subsequent milestones. Arguing that early adopters do not deserve to profit from this is akin to saying that early investors in a company, or people who buy stock at a company IPO (Initial Public Offering), are unfairly rewarded.

This argument also depends on bitcoin early adopters using bitcoins to store rather than transfer value. The daily trade on the exchanges (as of Jan 2012) indicates that smaller transactions are becoming the norm, indicating trade rather than investment. In more pragmatic terms, "fairness" is an arbitrary concept that is improbable to be agreed upon by a large population. Establishing "fairness" is no goal of Bitcoin, as this would be impossible.

Looking forwards, considering the amount of publicity bitcoin received as of April 2013, there can be no reasonable grounds for complaint for people who did not invest at that time, and then see the value (possibly) rising drastically higher.

By starting to mine or acquire bitcoins today, you too can become an early adopter.

One Bitcoin is divisible down to eight decimal places. There are really 2,099,999,997,690,000 (just over 2 quadrillion) maximum possible atomic units in the bitcoin system.

The value of "1 BTC" represents 100,000,000 of these. In other words, each bitcoin is divisible by up to 108.

As the value of the unit of 1 BTC grew too large to be useful for day to day transactions, people started dealing in smaller units, such as milli-bitcoins (mBTC) or micro-bitcoins (μBTC).

No, your wallet contains your secret keys, giving you the rights to spend your bitcoins. Think of it like having bank details stored in a file. If you give your bank details (or bitcoin wallet) to someone else, that doesn't double the amount of money in your account. You can spend your money or they can spend your money, but not both.

Bitcoins are divisible to 0.00000001, so there being fewer bitcoins remaining is not a problem for the currency itself. If you lose your coins, indirectly all other coins are worth more due to the reduced supply. Consider it a donation to all other bitcoin users.

A related question is: Why don't we have a mechanism to replace lost coins? The answer is that it is impossible to distinguish between a 'lost' coin and one that is simply sitting unused in someone's wallet. And for amounts that are provably destroyed or lost, there is no census that this is a bad thing and something that should be re-circulated.

In a Ponzi Scheme, the founders persuade investors that they’ll profit. Bitcoin does not make such a guarantee. There is no central entity, just individuals building an economy.

A Ponzi scheme is a zero sum game. In a Ponzi scheme, early adopters can only profit at the expense of late adopters, and the late adopters always lose. Bitcoin can have a win-win outcome. Earlier adopters profit from the rise in value as Bitcoin becomes better understood and in turn demanded by the public at large. All adopters benefit from the usefulness of a reliable and widely-accepted decentralized peer-to-peer currency.[4]

It is also important to note that Satoshi Nakamoto, creator of bitcoin, has never spent a bitcoin (other than giving them away when they were worthless) which we can verify by checking the blockchain.

As deflationary forces may apply, economic factors such as hoarding are offset by human factors that may lessen the chances that a Deflationary spiral will occur.

Inflation is simply a rise of prices over time, which is generally the result of the devaluing of a currency. This is a function of supply and demand. Given the fact that the supply of bitcoins is fixed at a certain amount, unlike fiat money, the only way for inflation to get out of control is for demand to disappear. Temporary inflation is possible with a rapid adoption of Fractional Reserve Banking but will stabilize once a substantial number of the 21 million "hard" bitcoins are stored as reserves by banks.

Given the fact that Bitcoin is a distributed system of currency, if demand were to decrease to almost nothing, the currency would be doomed anyway.

The key point here is that Bitcoin as a currency can't be inflated by any single person or entity, like a government, as there's no way to increase supply past a certain amount.

Indeed, the most likely scenario, as Bitcoin becomes more popular and demand increases, is for the currency to increase in value, or deflate, until demand stabilizes.

The members of the community vary in their ideological stances. While it may have been started by ideological enthusiasts, Bitcoin now speaks to a large number of regular pragmatic folks, who simply see its potential for reducing the costs and friction of global e-commerce.

This is true: see Weaknesses#Attacker has a lot of computing power.

That said, as the network grows, it becomes harder and harder for a single entity to do so. Already the Bitcoin network's computing power is quite ahead of the world's fastest supercomputers, together.

What an attacker can do once the network is taken over is quite limited. Under no circumstances could an attacker create counterfeit coins, fake transactions, or take anybody else's money. An attacker's capabilities are limited to taking back their own money that they very recently spent, and preventing other people's transactions from receiving confirmations. Such an attack would be very costly in resources, and for such meager benefits there is little rational economic incentive to do such a thing.

Furthermore, this attack scenario would only be feasible for as long as it was actively underway. As soon as the attack stopped, the network would resume normal operation.