Such as a lack of innovation or work incentive? Granted that it did not have the problems capitalism had, such as overproduction and unemployment, and it did not have an indirect social labor relationship. But how can a socialist economy compete with a world dominated by capitalism, in terms of infrastructure and revolutionizing technology? What if economic aid is cut off by revisionist countries, and if doing business with the bourgeoisie is considered "revisionist," how can you overcome this? How are you going to get people to work without compensating them for a lot of money? And if you can't give them money, how is the state going to be able to accumulate money to purchase goods for the workers?
Command economies should be far easier now due to great strides made in computing technology. You should PM Paul Cockshott for more info on this, since he's studied it.
