If they are arguing that, then it kind of makes their part 91 mute... because as soon as it is communicated that you are going somewhere (maybe even before - when you think about it?) then you have scheduled a flight so you should operate under 121?

I don't really understand what the big issue is... this currently happens. From what I understand it is not for profit but more of a split of fuel costs. If the pilot is going to some location just to bump up their hours why not take a full plane. The passengers must however take it upon themselves to understand the risks, as more than likely this pilot that is taking them is low on hours therefore an inexperienced pilot by international standards or just flying for fun/ a hobby and trying to make it cheaper. The pilot who is flying them must still be rated to take passengers etc. etc. etc. what is the big difference?