I am learning this as part of academics, but I belive Map reduce was introduced for handling google page rank and it seemed to handle it well, so SHOULD I SAY "USE HADOOP BUT IN A SENSIBLE WAY WHERE IT REALLY HELPS" or is it like never use it ?
And OP, if you see this, using raw M/R to do things like graph processing is going to be a HUGE pain in comparison to all the libraries built around it.