This is a good refutation of the linked article. The authors of the original article definitely seem to misunderstand both the purpose and the usefulness of MapReduce.

The claim that MapReduce is a poor implementation, for example, is particularly silly. Most large scale relational databases rely on very powerful centralized machines, and replicas of those machines. MapReduce, by contrast, relies on a large number of commodity systems. The decentralized nature makes hardware failure much less likely to cause problems. The system knows how to dynamically reallocate tasks, and new nodes can also be added while the system is running.