...just shows that Tor is really anonymous and safe.
It shows that the groups who go after and prosecute these people don't have the resources or motivation to get to all of them.
When you have a very significant target of the US (near the wanted level of Bin Landen) or China talking freely on Tor without getting caught, then perhaps you can rule it as being seriously anonymous.
I don't know about other countries, but in the US I generally only hear about people getting prosecuted for CP and similar crimes when they are caught in the act or when somehow the computer files get accidentally discovered or reported by some 3rd party.
This is an important point. The anonymity of Tor relies on finding safety in numbers (or rather, among numbers).
However, the bar doesn't have to be quite that high in order for Tor to be considered de-facto anonymous. There is an order of magnitude separating the resources available to a local police force and the entire DoD. Criminals guilty of capital offenses might only garner the attention of the former, whereas someone at a 'Bin Laden' level of notoriety would be chased with the near-limitless resources of a superpower's defense apparatus.
The feds conduct ongoing child porn investigations, not just passive enforcement. Once someone with CP is found, the feds often try to seize the provider in order to collect information on other offenders, which in turn leads to further arrests/prosecutions. And the cycle continues. I used to think Child Porn was rare. I was wrong.
It shows that the groups who go after and prosecute these people don't have the resources or motivation to get to all of them.
When you have a very significant target of the US (near the wanted level of Bin Landen) or China talking freely on Tor without getting caught, then perhaps you can rule it as being seriously anonymous.
I don't know about other countries, but in the US I generally only hear about people getting prosecuted for CP and similar crimes when they are caught in the act or when somehow the computer files get accidentally discovered or reported by some 3rd party.