I meant to say, but forgot, (Thanks ORaman).
The advantage to smaller files/multiple files for a tablespace is not only the parallel query OraMan mentioned, but overall performance can improve with the load balancing of putting the files on different spindles/drives (sets of spindles/drives if RAIDED.)
I am not sure (don't think that) it helps if you are on a monolithic drive or as in our case single channeled to EMC/SAN.
