I'm pretty sure some of the distribution bans were based off people reporting the person who gave them the hacks to lower the ban time, rather then true proof. But that might be wrong, maybe the committee saw more.
It'd be hard to get proof sometimes, like when I got banned and those modded maps were going through the entire vent I used, alot of it was people private chatting saying: U WANT THESE WALLHACKS? HERE YOU GO!!!!! LINK!!! . Pasting ventrilo logs wouldn't be that legit or trusted just like IRC logs. Seeing as the whole clan had the same hack, and used them around the exact same time, you should realize theres a distributer and there should be something to look into. But unless 'somebody' had logs or email you wont be able to find that much proof.
I had logs from two of the currently banned players saying Br55HiT gave them the hacks, at different times... but then my computer crashed and everything got deleted. But logs get you nowhere, or they do 'sometimes' but not all the time who knows. I wonder what the true proof on most of the distributers hmm, seeing as logs were considered not legit...