On some
furling systems (mine included)
line is attached by going through a hole tangential to the drum center and then a knot on the end. It would be difficult to imagine this coming undone. Also, consider that force on the
line is proportional to size of the leverage, and since
furling drum radius is much smaller than length of the sail, force on the
line is proportionately less. It may be a significant force nevertheless, but hardly beyond what even a basic
line can handle.
However,
furling can certainly fail in variety of ways - no doubt about that.