Yes, what about the children? If you care about the children, it's not the internet you should be worried about:

A few years back, the NSPCC (a UK child protection charity) released a study that claims that 75% of all child abuse, including sexual abuse, is carried out by a male adult related to or known to the family. The most likely abusers are the dad, brothers and uncles, followed closely by other male relatives and friends of the family. Random strangers come far down the list.

> Why is a world with ideally zero ability to prosecute child porn (to pick one)

Why do you think there would be zero ability to prosecute child porn? Given the above, it would seem that the best investment in prosecuting child porn would be in addressing the problem at source: Better monitoring of children's health and wellbeing to increase detection and prevention of abuse in the first place, rather than trawling through peoples communication.

Of course that won't happen, because parents will all believe that their spouses and relatives and friends could not possibly be abusers, and of course most of them will be right, even though reality is that they pose by far the greatest risk to your child. Random strangers are just even less likely to harm their children.

Before we sacrifice privacy even further, we should at the very least have the facts as to what effects altering the privacy balance could actually have. Is there any evidence that more aggressively pursuing child pornographers online makes much difference to actual harm as opposed to moral outrage?

Even so, even if we allow 100% privacy in communication, people get caught for child porn possession all the time without having law enforcement violate their privacy first: Spouses report pictures from their PC; people stupidly hand their PC in for repair and it pops up; people get caught actually abusing children etc. In which case their sources are often revealed. In which case the police can do actual police work, and set up stings or visit any sites that person has obtained child porn from, and get those sites taken down, and follow the leads to payment processors etc.

In fact, a number of large child porn sting operations were conducted in exactly that way: Unravel sites where the site itself was blatantly illegal, and then track down users/customers.

I don't know if the person earlier in this thread wants to be absolutist about the privacy, but for my part this is one area where I draw the line: If there is a legitimate case against one party to a communication, then I don't see a problem with having the police go through the logs of such a site, or the e-mails of anyone implicated and tracking down any regular users or customers of such a site - I don't see a good privacy argument against that.

But note how different that is from accepting interception of communication using a site that has entire legitimate uses, and where there is no evidence of wrongdoing in the case of most of the users prior to the government request to intercepting everything.

Even when there's no malicious intent, the chance of serious errors skyrockets when you start allowing these kind of tactics where criminal investigations becomes playing the numers too. Check Operation Ore, for example, where a long range of errors conspired to make what started out as a database of card transactions, some of which were to child porn sites, ended up being treated pretty much as evidence of purchase of child porn. Problem was tens of thousands of the cards appearing in the database were stolen, and a large number of the transactions were for legal sites; the resulting operation caused several wrongful convictions, and far more ruined lives and children taken out of their homes for the wrong reasons. The operation also has resulted in dozens of suicides (though it is unclear how many of the suicides were innocent people, if that matters to you).

It underscores that even if were are 100% ok with police invading our privacy if they make no mistakes, the importance of considering the potential damage of false positives must also be taken into account: If the crime being looked for is rare enough, it is perfectly possible allowing "dragnet" type surveillance to clamp down on the crime will cause more damage through investigative errors than it will prevent. This is another important reason to be careful about giving up on privacy.