A Petzl I'D is available for people silly enough to thread things wrong I believe. Also, you shouldn't be unclipping your cowstails until you've tested the Stop, that's partly what they are there for. If you follow standard practice you can't do it wrong really. Of course some idiot can go out and buy all the kit, not bother getting shown how to use it, or even read the instructions, do it how he THINKS he should do it, and die.
However, as with all potentially dangerous activities, you should seek proper training and practise until you are confident before deciding to take on the 'real thing'. I wasn't fotunate enough to know proper cavers when I was interested in learning SRT so instead relied on friends who are IRATA technicians and guys who work in my local climbing/caving shop to show me and give me pointers, and dvds to learn some of the other stuff we couldn't cover. I practised all above ground, starting with ascents of just 3m.