Isn't is possible that the sample is biased because you only looked at the subset of traders who were not sophisticated enough to turn off the feature that allows others to observe their trades?
Not disagreeing - but it's worth noting that you _always_ want someone to take the same trade as you, right after you do.
This is a good point. And we shouldn't assume this means that the number of successful traders is automatically higher due to their greater understanding. There could be a large number of people hiding their trades due to a losing record, or an unlucky streak inducing paranoia.