Good and Bad.
Good in the sense that they are doing something neither the police or the government will do.
Bad in the sense that if they are wrong, an innocent person could end up getting attacked and killed by a lynch mob.
I hate this culture that has spawned on Facebook - you know the type, you see a picture of somebody with a caption saying something like this is 'whoever' - he is a pedophile and has had sex with over 100 babies, hit 'like' if you think he should be hung. you then get millions of people 'liking' it and posting comments like 'filfi peado scum, ope u rot in ell' or something like that.
The chances are that the person in the picture is innocent and the subject of a hate campaign because he pissed his ex girlfriend off... but stupid people believe it 'because it was on facebook' and the guy is forever watching his back from lynch mobs trying to kill him...