- Many sites are hosted on massively shared hosts. Blocking those IPs will cause a lot of services to be unreachable, not just the one to be blocked.
- People find you with your domain name, not your IP, so a service could avoid filtering by switching subnets every day and just keep updating the DNS entry. After a certain time, the govt will be blackholing a large part of the internet.
(Though that was more incompetence by network engineers than legitimacy of the method)
[1] http://www.ripe.net/internet-coordination/news/industry-deve...
There are a lot of businesses that have to deal with outlandishly high rates charged by companies that process credit card payments for non-US companies. I'd find it far more convenient to send a bitcoin payment to a supplier in China than have to go to the bank and handle the conversion that way and would also love it if I could exchange BTC for HKD or CLP the next time I'm travelling in Hong Kong or Latin America.
Assuming BTC becomes a generic unit of exchange, the currency promises to save me around $50 to $100 per international money wire and cut the time it takes to transfer funds down to a few minutes. I've had zero failures using the system to date (max transfer time of 20 min), and would need to see a 10% failure rate before it stopped making sense. And that's without even calculating the costs of relying on monopolistic intermediaries like banks for currency exchange.
In practice, it takes within about 10 minutes for the first confirmation to go through, and 10 more for each one after that. Most merchants will likely be interested in waiting for a few more blocks to be added before totally accepting, but that can be solved by middle-men that provide insurance against double-spending, allowing immediate transactions. And transactions move across the network quite quickly - I tend to see them appear well within a minute.
The moment you send out your transaction (assuming it's valid), you can consider it approved, and move on with your life. The recipient can also acknowledge the transaction within a minute or so at most, it's the network validation and protection against alternate transaction histories that takes time.
Also you'll need a different way to do the initial currency distribution which is also cheater-proof.
These are very hard problems.