Why the IBM and Twitter Data Deal

It has been presented as a means to understand the pulse of the planet.   A sensory coup previously impossible.  Connecting the firehose of information created in twitter with the analytics and cognitive capabilities of IBM.  It certainly makes me think.  Is the data represented by Twitter, and other sources, clean enough, precise enough to provide quality predictions?  Good introductory interviews in Fortune,  which don't answer these questions, but address the motivation and possible first steps.  Watching.