If that was the test, you could get a lot of people in trouble by causing their browsers to cache images that aren't displayed to the user. They'd never know it was there until the cops kicked in their doors and searched their computers.
Which makes it a wonderful law to have in place for a Socialist government interested in taking pre-emptive action against political threats.
even better, if you are using an unpatched version of internet explorer, you could view an image on a normal site and have a virus installed on your machine. that machine could turn your machine into a 'bot-zombie'. basically running their program whenever the machine is turned on and logging into an irc channel. from that channel, it can recieved commands that it will execute... like 'cache and server these files'... which could be anything.