re: Neither the Theory or Reality is suitable

1) mOst are pretty good heuristics, and work well enough. those that do defeat current spam filters for any length of time are usually emails with imagemaps instead of text. Email clients should have "download pictures automatically" turned of by defualt.

2) That would not stop malware-laden attachments sent by scanning address books, adn most people have attachments set to not automatically download to save bandwidth.

3) Microsoft securtiy is what gave us Vista (partly). More of it is not a good idea.

4) ISPs should not do this. It should be part of the National Curriculum for say year 10s, and the manual freely availible from public libriries or somewhere similar.

Like in the Wild West, you should look after yourself, and if you think you can take down a scammer or spammer without getting your sytem wiped out or harming inocent bystanders, then you should be allowed free rein to do so.