Well no doubt China is a big country with a billion people. Maybe some people in India thinks that only India is a big multi-cultural, multi-ethnicity country which today faces the challenges of internal security threats like Maoists, insurgents in NE states not counting externally motivates terrorists etc.
In case of China , it has grown imperialistically in the days of Mao when its "annexed" states like Tibet, Xinjian. I will not go in the argument if theses states were historically part of Chinese empires. But clearly culturally these states were totally remote from the Han culture of mainland China. Now that was history i.e. 60 years back. The events that are happening in these regions are a result of unsound policies followed over the last 60 years by the Communist Party of China.
Since the regions of Tibet and Xinjiang were totally culturally distinct from the mainland China, Communist party devised a policy to slowly trying to change the demographic profile of such regions which are administered "autonomously". In the past 60 the Han population in Tibet and Xinjiang has been increasing so that China has more firm control over these regions. China has pumped in money from its rapidly rising economy in these regions establishing semi-military government organizations like XPCC (Xinjiang Production and Construction Corps). Qinghai-Tibet railway is also an instrument for the same purpose , though its benefits and strategic implications are numerous.
The reason these two states are important for China is that Xinjiang is rich in Oil and other mineral deposits. Tibet has its own strategic importance , it is not for nothing that Tibet is called "the roof of the world".
The main cause of unrest in Xinjiang is that the ethnic majority of Muslim Turkic peoples like Uyghurs have not received equal treatment as the settled Han people have. This is partly because there is language and other social barriers for the Uyghurs people have made them second class citizens in their own land. The ever increasing population of Han people in Xinjiang has alarmed Uyghars. There is constant crackdown on any kind of protest or attempt by Uyghars to voice their discontentment.
If we see how China deals with any protests then some patterns emerge. First the government try to control the unrest using armed police force and enforcing prohibitory orders. This results in more stronger form of protests , resulting in local authorities retaliating and in case of Xinjiang it resulted in around 185 dead and several thousands injured according to some reports.
Not only this China has a well oiled state machinery which start demonizing the protesters as soon as some unrest starts. Mouthpiece of Chinese Communist party tried to project that Uyghars and one of their organization has links with Al-Qaida. Rumors where spread in Xinjiang resulting in direct clash of Han and Uyghar peoples in Xinjiang.
Though Chinese premier sensed the urgency of the situation and returned back home from G-8 summit.
The importance of Xinjiang is quite high when we consider the location and resources of this autonomous province. Xinjiang is rich in oil and mineral deposits. Its geo-political location is also quite important. It borders Tibet, Russia, Tajakistan, Kazakistan, Krygystan, Afganistan, Pakistan. This location is sufficient reason that might lead to raising the interest of superpowers.
In short the whole policy of Communist Party to change the demography of a region is affecting the aspirations of local population. To make matter worst the government has no avenue for peaceful settlement of genuine issues of its citizens.
It is an irony that the money that communist party is pouring into such endeavors is resulting in weakening internal security situations in different provinces.