mlib versus spark

[Saikat Kanjilal]

Ok I'll admit I'm not seeing what the obvious differences are, I'm a bit 
confused when I think of mahout using spark, since spark already uses an 
embedded machine learning library (mlib) what would be the impetus to use 
mahout instead, seems like you should be able to write or add algortihms to 
mlib and use spark, has someone from mahout looked at mlib to see if there will 
be a strongusecase for using one versus the other?
http://spark.apache.org/mllib/