Here's the rule in the 2002 NEC that prohibits a box with knockouts to be used in the manner described. OSHA would also cite them because of their concern about open knockouts. This has been a long standing rule for a long time!
314.23(H) Pendant Boxes. An enclosure supported by a pendant shall comply with 314.23(H)(1) or (2).
(1) Flexible Cord. A box shall be supported from a multiconductor cord or cable in an approved manner that protects the conductors against strain, such as a strain-relief connector threaded into a box with a hub.
