There are many questions to be answered in this incident.
First of all, why would China agitate Vietnam at a time where it is already having a plateful of territorial troubles with Japan and to a lesser degree, the Philippines? Such action yields very limited economical benefit all the while sending its neighbors further towards Camp USA. At this rate China would never be able to break the US's Island Chains through diplomatic maneuvers.
While stirring nationalist rhetoric has long been the tool of choice for CPP when it comes to distracting public attention away from socioeconomic issues, this latest incident happened at a rather peculiar time considering China's domestic opinion regarding Vietnam is recovering following Vietnam's extensive effort in the recent search and rescue mission for flight MH370.
Therefore it is very likely that this is an unintended result of factional in-fighting within the CPP, similar to the North Korea's torpedo incident in March 2010 when Kim Jong Un was struggling to consolidate power.
Secondly, from Vietnam's side, the handling of the incident so far has been adversary to its economical interests, which is an interesting and alarming approach.
China accounts for a quarter of Vietnam's tourism industry and Vietnam relies heavily on China's natural and industrial resources. If CPV does not moderate its tone against Chinese assertion in the South China Sea, it will be very difficult for the government to wind down anti-China sentiment when they start feeling the economic pinch. Not to mention the current indiscriminate vandalism against foreign enterprises will likely contribute to an exodus of FDI, something that Vietnam has been working very hard competing against its troubled neighbours in recent years.
Right now it seems China has an upper-hand in terms of military and economic strength. It also looks like the CCP is taking a page out of Tokyo's island-grab manual where (a superior-armed) Japan has operated oil rigs for decades in the disputed waters around Diaoyu Island under the assumption that a poke here and there does not warrant the weaker side of the conflict to start an all out war.
It is evidently a lose-lose scenario if the situation continue to escalate. However amid the chaos there lies vested interest from both sides that would benefit from this. We may never know who and why, but it is up to the ruling governments from both sides to rein in those fanning the furnace while treading carefully in those contested waters.