My background - 4 weeks old in the Hadoop world. Dabbled a bit in Hive, Pig, and Hadoop using Cloudera's Hadoop VM. Have read Google's paper on Map-Reduce and GFS .
I understand that-
Pig's language Pig Latin is a shift from(suits the way programmers think) SQL like a declarative style of programming and Hive's query language closely resembles SQL.
Pig sits on top of Hadoop and in principle can also sit on top of Dryad. I might be wrong but Hive is closely coupled to hadoop.
Both Pig Latin and Hive commands compile to Map and Reduce jobs.
My question - What is the goal of having both when one (say Pig) could serve the purpose. Is it just because Pig is evangelized by Yahoo! and Hive by Facebook?