Innovation on the internet is often free of third party harm. Bitcoin looks to be internet only but it also presents itself as a money transfer service and an investment service. Which as seen in 2008 can be used for fraud with big consequences that the average person can't always understand.
Given the hassle of having to drive around I can imagine cops being annoyed.
The obvious answer to this is mandatory disclosure with a selectable delay on certain information, to the shops about when searches are made and if a single item in their shop was looked at.
All searches should have a generic id number for shops who want to raise a grievance. And the police should have to fill out case paperwork online getting a case number that allows for a search. Then all keywords searched and items viewed should be attached to the case automatically if they need to be viewed. You could even attach results, it is not as if harddrive space is expensive anymore.
If German youth actually read erotic ebooks that they can purchase without their parents credit card, this will just lead to more video porn, camming which some will record and put online, and actual sex.
I get the feeling some of these people still haven't tried the internet yet.