Over at GridGuru's they have a interesting article
regarding Map Reduce its applications. The Map Reduce crowd has been growing of late and is out spoken about what a great tool it is. Without a doubt it is, but something I learned a long time ago is that for each job there is a correct tool. You don't use a sledgehammer to fix your watch and you don't use a pair of tweezers for demolition.
I am a skeptic, which is not to say I have anything against a generalized framework for distributing data to a large number of processors. Nor does it imply that I enjoy MPI and its coherence arising from cacophonous chatter (if all goes well). I just don’t think MapReduce is particularly "simple". The key promoters of this algorithm such as Yahoo and Google have serious-experts MapReducing their particular problem sets and thus they make it look easy.
Sadly this implies that processing data in parallel is still hard no matter how good of a programmer you are nor how sophisticated your programming language is.