You know, I find this whole thread unbelievably sad. I work in a field where liability is a constant specter, looking over my shoulder. Worse, it's real; in my profession, the average is that you will be sued every 7 years. I've been lucky until recently.
In contrast, the NUMBER of suits filed against dive buddies, compared with the number of dives completed or even the number of incidents, is extremely low.
I go to work on a regular basis, knowing what the odds are against me. I also dive with all kinds of people, some of them highly skilled, and some barely out of OW (I have insurance for the ones who are IN open water!
) When you start letting the remote possibility of a lawsuit keep you from enjoying a pleasant dive with a buddy, that's tragic. If you have doubts about the capacity of an instabuddy, set parameters for the dive within which you feel you can manage most if not any issues. A friend dove as a mentor with a new diver a few weeks back -- the diver lost his primary regulator, could neither retrieve it nor remember where his secondary was, and would not accept a reg from my friend. As a consequence, he took the shell-shocked diver to the surface quickly, and no one was harmed. (My friend has rethought diving with beginners, though, which is sad.)
If you want to dive solo, do so. But please don't use legal liability to legitimize your choice.