Restricted to the publically-available data from one particular and rather odd site, but probably not crazy. At first it seems counterintuitive, shouldn't it be roughly 50% gaining and 50% losing? But I guess that people typically put in a modest amount of play money, and then tend to trade until either they run out or get discouraged from losses.
1) They aren't trading against each other (they're trading against professional investors)
2) When you trade randomly you should expect to lose money (paying fees, paying spread, getting 'good' executions rarely and getting 'bad' executions often, etc.)