I reported on this here:
viewtopic.php?f=1&t=48963 which article includes link to the original study.
And Jeff reported on the study and several other studies of a similar type here:
viewtopic.php?f=22&t=32434&p=504079#p504079 (13th article in thread and 4th reference)
But your right, not only might there be a washing away of other nutrients/chemicals, but it also seems wasteful of precious water. On the other hand, in the same link above from Jeff, further down the thread, it does seem all the arsenic scare in rice needs to be put in proper perspective.