Systems like Leisure Furl still allow you to drop the sail even if the mechanical system were to fail. (I'd never get a boat with in-mast furling, or behind-mast furling.)

However, even traditional running rigging can fail -- I read the other night about a sailor whose mail halyard sheave somehow allowed the halyard to get jammed into a space between the sheave and its opening, while the sail was up. Fortunately they were able to get it lowered enough to reach it from the bosons chair on the spin halyard, and cut the main halyard to lower the sail... Also fortunate conditions were calm enough for that.