How efficient are FBI entrapment tactics?

M.N.: I have to comment briefly on the previous post:

"The known facts from this latest case seem to fit well within a now-familiar FBI pattern whereby the agency does not disrupt planned domestic terror attacks but rather creates them, then publicly praises itself for stopping its own plots." - Latest FBI Claim of Disrupted Terror Plot Deserves Much Scrutiny and Skepticism 

Personally, I feel intense and instinctive dislike for one of the more known authors of the cited article: the notorious Glenn Greenwald; however, I must say that he makes a point here, which is presented clearly and logically. For me, the questions are, first of all: 

How efficient are FBI entrapment tactics? and

How to measure FBI efficiency and performance?

I suspect that the entrapment tactics (especially in individual cases) are not very efficient, or not always, or not in majority of cases; in terms of their overall impact (and this might be one of the reasons for the critical, alarming state of the current anti-terrorism situation). Furthermore, they might breed terrorists and expand the terrorist activity due to radicalisation in the U.S. prisons, which might be instigated and exploited by the hostile intelligence services. 

These tactics might be counterproductive, a distraction, a waste of resources, and a generator of bad publicity rather then the good one. They might be an outdated carryover from the previous styles of work and operations of the times past. I think, it would be a good idea to look into this issue "scientifically" (in quote marks because it might be very difficult to design such a "scientific" comparison study/es). Intuitively, it feels that the provoked, induced socio-legal experiments have random and sporadic character and therefore are less representative of these phenomena (and less efficient in corrective interventions) than the large scale non-provocative, observation (mass and targeted surveillance and careful patterns and trends analysis) based tactics.