I'm not blaming Google/Paypal etc, but just as we all have to be accountable for our income at some point, so should they. They should not be earning from illegal activity.
The shoplifter analogy doesn't work as you wrote it - if the shoplifter on the way home gives the bus company some proceeds from the crime, the bus company knowing the source of the income, should they be held to accountable for that income? of course they should. Is it proceeds of crime - yes it is.
Take pirate music as an example. End users thought it was free- but massive amounts of money was generated by pirate music sites. KimDotCom etc didn't get stupidly rich from the people downloading pirate music files. He got rich from being paid a share of Ad-click revenue. He was paid by Google for example. So Google also made massive amounts from illegal file sharing. How is that OK? We all woke up to that way too late.
Google (etc) benefitted hugely from stealing income from musicians and songwriters and got away with it for a very long time. Nowdays, the music biz has finally woken up and now "free" music sites such as youtube, spotify, pandora etc all have to pay a share of this income to various collections societies who distribute it to the people who actually own and performed and wrote the music and other content these companies monitise. It's still far from perfect, but they are addressing it with some success.
So just to say "it's impossible" - I don't accept.
I think it is possible but we haven't found a way yet. More pressure needs to be put upon the organisations that control the internet. The claim that internet is an uncontrollable wild frontier of personal freedom is a myth. It is increasingly controlled and monitored and most importantly monitised, on many many levels.
It's simply that the abuse of children and trading in those images, is not a priority - it doesn't generate enough money.
Porn is a massive part of the internet, and is a massive economy. More pressure can be put on that industry to self police.
But govt etc don't want to put legitimate pressure on these online industries to clean up their act re their involvement with child abuse, they don't hold them accountable.
We are experiencing just the beginning of the internet - it's not going to go away. To say it's too hard just doesn't cut it.
Bertie I agree completely with your points about tracking child abuse might interfere with legitimate experiences of using the internet. But that just proves the point that children are at the bottom of the heap re having any power in our society, and it's OK to prioritise everyone else over them.
I'm not for a minute suggesting that this is just a UK problem, and just the UK has to address it. THere are many international trade agreements and alliances and organisations that would be more involved. But again it comes back to money and power leading the motivation.