I agree that a lot of young riders have poor brake technique. I have a 24" with a standard Magura, Plaz pads, no booster, a 3 year old grind so worn beyond smooth, no tar and a fairly shoddily setup brake really, and I'm a fat f**ker, yet I have no problems with my back brake holding.
You go on rides and there's 14 year old kids with super light mods who must weigh half of what I weigh, with all these fancy new pads, mega booster, rims grinded the hell out of that morning, yet they are still bitching because their brake is slippy. Either they aren't using any pedal pressure at all or they can't pull a lever to save their lives or they simply aren't getting near the top of things and are being delusional and thinking its the brake.
Everyone should have to ride with shit brakes/no brakes at some time, it does make you better.