[Drag]

No one bothered to make a really compelling case, but IMO it can be created quite easily.

Something along this line:
If we assume that there were no cheating, and we futher assume that the players in question played bad and should be losing at a rate of about -20PTBB/100 in NL, -3PTBB/100 in Limit, and they have less than avrage probarility of winning a tournament (if there were 1000 palyers it would translate to 1/3000 probability of winning it). Then we take all the hands that they played in NL >1000, Limit >1000, and take into account a tourney won, we'll get a probaility of such an event of bein much less than 10^(-8).

We need to take into account that there is less than 10^3 players who play at these stakes, and high-stakes on-line poker exists for ~4 years, so there were about 4*12*1000 ~ 10^5 month of play (it's better to reformulate it in terms of hands played, though). So the probability of such an anomaly is less than 10^(-3).
And I am taking very conservative estimates.
So we can falsify a hypothesis that they played honestly.

So, what we get is that probability of someone having such a run by sheer luck during all time of on-line poker existence is less than 10^(-3). For me it is very compelling.

There is additional information that could be incorporated which will lower this probability even further, like the evidence about individual hands play, but I can't see an easy way to do so.