I also agree with what you (half jokingly perhaps) referred to regarding psychology.
Just as an exmaple, imagine several signs, one after the other. Friendly, welcoming, but each urging (some might say begging) people not to climb the monument. Something like that would make the guillt of ignoring those pleas quite large in most peoples minds.

Its fairly easy to get people to do/think what you want, you just have to know the tricks I guess.