If I change a tyre for someone I try to teach them how to do it as well.
Once I had a flat tyre and friends on board helped. A few days or perhaps a week or so later (before I fixed the tyre and swapped it back in) I heard a noise coming from one of the wheels. The nuts were on backwards and had worked their way loose so that the wheel was starting to wobble.
Obviously whoever taught your friends how to change a wheel didn't do a very good job.
I'm sure when you are teaching someone then putting the nuts on the right way round is part of the learning process. If I am able to I usually try to explain why something needs to be done a particular way, in the hope they might remember it better when the time comes that they have to do it by themselves (without tuition).
babola: "Enjoy your tools and don't be afraid to air your opinion and feelings here, but do it in courteous and respectable way toward others, of course."