From a research standpoint, it's nearly impossible to ascertain the exact numbers, simply because of the nature of the investigations. Hence the limitation on my thesis research. lol
My personal estimates, at least in my own state, are pretty high in terms of infiltration rate. Historically the alphabet agencies have a trend of infiltrating and even controlling entire movements, and I think that very well may be the case here.
What I would disagree with you on is the 'ineptitude of the system of policing.' While we may see this for the crappy tactic that it is, and the overall incompetence of the justice system at large, it's also a testament to something far more insidious than simple ineptitude. They're purposely choosing emotionally vulnerable, easily manipulated targets, for the purpose of cultivating and exploiting them, and getting them to commit the crimes that the rest of us aren't committing. That's evil...but I cannot get past the part where we always have a choice. Even the vulnerable, even the easily manipulated, even those with lesser intelligence who can't tie their shoes, have the ability to say no. Free will coupled with responsibility is the hallmark of liberty, is it not? I think it's a cop out on some level to simply say it proves ineptitude. I think it actually proves far more than that...and I also think we need to do a better job hardening our minds against such exploitation.
RE: Does Entrapment Really Make Good People Do Bad Things?