For those not aware, China has a nationwide firewall in place called the Golden Shield Project that’s also known as the "Great Firewall of China" (in reference to the Great Wall of China). China can and does block things on a nationwide basis routinely.

The reason for the blocking of YouTube is because of the footage present showing protests in Tibet.

So why should you care?

China does affect how the internet works as a whole. On several occasions there have been large internet companies that have made concessions based on China’s wishes.

Why would any large internet company do this?

Because China is right behind the USA in internet users and catching up fast; it’s a market that can’t be ignored based on sheer numbers.

If you happen to operate a business on the internet with an international customer base and serve video via YouTube solely, you may want to consider alternative video sites or host video on your own domain instead.