simbrooks:II agree with your examples, except that when being instructed you should work up to the new skill/experience - expanding slowly, not big leaps, you shouldnt have to trust your instructor to be able to do the dive during a course. They should help slowly increase your skill/comfort/experience, but shouldnt be relied upon for anything more than instruction and to be a buddy (or in some cases a casual observer if there are a couple of students diving together). Not saying i dont trust my instructor(s), but when we plan we do it together, or rather the stage is set and i work it out, but he already knows the answers We work through scenarios, work up to the new dives and make sure i am capable before moving along.
Well said, but that's part of trusting your instructor. Your instructor should be familiar enough with your level of training and experience not to put you in a situation you're not ready for. How will you know if you're ready for it or not if you've never done it?
As of UP's example, could your buddies get out of a situation by themselves if the situation arose, or would they need to rely on you to get them out of it? If you have to "hold their hands" throughout the dive (which I doubt you would take them on it if that were the case), then it's a trust me dive. If something goes wrong and they can "rescue" themselves, then they're competent enough to do the dive and they're just relying on your knowledge of the area to make it safer.
If s*** hits the fan and you need the assistance of your buddy to get your out of it because you don't know how to, then it's a trust me dive as I've always thought of it. If you have enough training and experience to KNOW how to get out of it, you may still need assistance (help with disentanglement, etc), but you're competent enough to be there.