I will have to agree with gfretwell; when the appliance is likely to be physically moved (as with a dishwaser), and not simply vibrating (like a transformer), I believe that it is wise to run a grounding wire.
his also applies when the flex is likely to be snagged, or tripped over, etc. I've just seen too many connectors -especially "jakes"- come loose. Indeed, I will often install liquid-tight for this reason; their connectors are more substantial.
