For one, having known many posters on wsb personally, the number of people actually trading large positions vs the number participating in that forum is not the same.

Finally, people (apparently even the "informed" crowd here) greatly overestimate the difficulty of identifying individuals or actions in massive systems that are effectively recorded and completely surveilled, and they underestimate the resources of the feds. It's usually not that hard to whittle down to a handful of actions, and even if there are hundreds it only takes a tiny bit of taxpayer money to comb through it by hand.