I have seen in one organisation instructors signing Part 3 of maintenance releases for solo pilots when they haven't even left their briefing room, let alone conducted the inspection they are signing for; now that is a time when they could find themselves in a big fat world of hurt. When I questioned this practice I was told "that signature is me authorising the student for the solo flight".. err....ok, good luck with that.
That's a rather damning indictment on the standards of training, testing and supervision of those instructors.