Am now thinking that it can actually be even simpler than I first thought.
Consider the following:
1) Extract a list of international airport codes for all major countries (there are over 2000 to choose from but perhaps half of these would be sufficient).
2) Extract lists of ISBN numbers for books and UPC codes for DVDs (no idea how many but obviously a lot).
The user is prompted to remember a film they saw or a book that they read from a holiday that they took (or break they were on) that sticks in their mind (but not so much because of the film or book itself) and after picking the relevant UPC/ISBN by selecting the title of the film/book (where they could also filter the titles by year) they would then next from a map of the world select the country and city (effectively choosing an international airport code).
Now they are instructed to write down an obvious (to them) clue about the occasion that they were watching that film/reading that book which does not include its name nor the name of the city.
Here is an example (taken from my own memory):
Clue: Home of the Shart
Code: PEK794043554223
Even if you knew me very well I very much doubt from that clue that you would be able to get that code (my wife doesn't get it at all and my family would have even less of a chance).
![Smiley](https://bitcointalk.org/Smileys/default/smiley.gif)
P.S. It is quite interesting that the typo pointed out from the OP is in my clue - it was no doubt this (Freudian?) slip up brought up a recent memory which I used to then then link back to a more distant one.