Illustration by Marius Watz
MapReduce advantages over parallel databases include storage-system independence and fine-grain fault tolerance for large jobs.
Related blog-based commentary is available at
http://www.searchenginecaffe.com/2009/12/dean-and-ghemawat-strike-back-on.html
Related blog-based commentary is available at
http://www.genomeweb.com/blog/defense-mapreduce-bioinformatics
A dialog between the Database researchers and Industry engineers is helpful.
For different use cases, users need different solutions. Scripting languages can be used as glue for different low level languages. Map Reduce and related tools can also be used as glue for different data storage & processing systems.