I have *occasionally * used shields very successfully for moms who were
ready to quit and it was a means of getting the baby to the breast.  Some
infants I find can't figute out to cue by drawing the breast back, they
are not refusing the breast.  Yes it's usually due to confusion or
preference, but I have seen them work in specific situations.
I agree in the hospital, Judy D., they should be kept under lock and key,
we still occasionally get a mom referred to us that was instructed on
using a nipple over her breast!!!!!