CRM doesn't just have to deal with only multi-crew aircraft. The principles can be applied in the single pilot cockpit. By this I mean that your pax can be used (in certain circumstances)to help out in single pilot ops. It's more efficient to get them to help in traffic avoidance (lots more eyes). I don't mean that we rely on them, but they are a good resource that can help us. There have been times when I've had my head in the cockpit momentarily, (to change freq's on the radio, get a map, look in the CFS, etc) and a pax asked if I had seen the aircraft on the left (or some other possible hazzard). I tend to think of it as managing all of the resources available to me.
Initially CRM was developed for multiple person crews, but we single pilot types can use elements of CRM in our cockpits. Obviously, some of its elements won't be applicable, but we can learn, and use the ones that do apply.
Cheers
Randy_G
If you can't stand the heat...
then turn up the air conditioner !! 