I read Sim Wong Hoo's book back in 2002 and thought this metaphor was really apt to describe what he was talking about - the fear of expressing oneself without express permission by authorities.

However, although it still applies to a certain degree, Singapore and Singaporeans in general have come a long way since he coined the term. People are more willing to take risks and question authority these days. A simple way to highlight this is the dramatic increase in the number of entrepreneurs here - which by definition refers to someone taking risks and pushing the envelope when required.

Anyway, here's the excerpt from his book on NUTS, where he explains what he means and gives examples: http://bit.ly/nouturn

Maybe it'll help elucidate why he coined the term and help decide how much it still applies.