The media is making mountain of a mole on the rift between Congress and DMK on the seat sharing formula. The congress was expected to do this since they themselves have more than 200 seats and hence are more powerful than 2004. In 2004 to form a coalition govt it was forced to give big money making ministries to DMK but the case is different today.
There can be no instability due to DMK. They have already told that they would provide outside support and DMK cannot withdraw support to congress even if it wants to since its own government in Tamilnadu is dependent on congress as DMK government here is a minority govt.
Even Jayalalitha is waiting for something like this to happen and hence DMK has to accept the fact that congress will act like a big bully this time. Hence market should not fear any instability at Delhi.