I don't think the coincidences are a sign of weak writing, Peggy. There is a time-honored tradition, going back at least to Shakespeare, of interweaving the lives of the principal characters in drama and fiction. More recently, the films of the American master Robert Altman frequently draw on that tradition. I would also add that in my own life as an analyst and therapist, I am amazed at how I end up running into people that my supervisees and patients tell me about.
Regarding the paramilitary nature of the mob that Phil brings up, I have noticed how often Tony uses military analogies. He tells Dr. Melfi, "We're soldiers." He watches the History Channel and loves World War II documentaries. The fact that Carmine is asked to mediate and ultimately chooses to tax Ralphie rather than whack him for his bad taste in humor reflects a military-type bureaucracy that is in stark contrast to street gangs.