I just had to add that I love Rick Fielding's comments above, when he explains why people sometimes arrange private sessions, "They're often not running away from those with lesser music skills, just lesser social skills." This is the crux of the problem, in my estimation. Our musical abilities and experience varies widely, at most sessions ... but that is not neccessarily cause for conflict. Our social skills, on the other hand, also vary considerably - and in the freewheeling environment of an open jam session, this fact is a frequent cause of conflict. It will surely test your leadership skills, if not your tollerance threshold!