Snuff films are as real as they get: any murder recorded on film is at its core a "snuff" film. The only direct organized crime connected snuff films would be those videos where Mexican cartel soldiers start decapitating each other with chainsaws, machetes or bowie knives.

Most films that can be qualified as snuff however are the work of unrelated vile pieces of filth that like to tape a murder for their own disgusting pleasure. A notorious one is the infamous "Three Guys One Hammer" video where two of the worst examples of inhuman garbage disgustingly slaughter an elderly man on film. Never watched the clip (you probably can find it somewhere on the internet), but the story surrounding it was enough to throw me into a fit of rage.