[KaiserPro]

From what I recall Map:Reduce was basically a weird representation of DAG based pipeline.

I think because it looked sorta like an automatic dictionary to multi-thread converter it became popular. But its pretty useless unless you know how to split up and process your data.

basically, if you can cut your data up into a queue, you can MapReduce. But, most pipelines are more complex than that, so you probably need a proper DAG with dependencies.