"Deterrence is the best method for preventing an illegal or unethical activity."
"Generally agreed that laws, policies and their associated penalties only deter if three conditions are present:"

• Fear of penalty
• Probability of being caught
• Probability of penalty being administered

• Fear of penalty
• the person thinking about doing the crime, has to fear doing the time. 
• punishments such as day parole, or non-prison time sanctions might not be strong enough to stop someone

• Probability of being caught
• the person thinking about doing the crime will proceed, unless the believe there is a strong chance they'll actually get caught
• fear of the punishment doesn't amount to much if they believe that the security forces are not good enough to actually catch them

• Probability of penalty being administered
• the 3rd stage of deterrence is the belief that if I get caught, and there is a penalty, I'll actually have to serve the penalty
• many people are under the impression that computer and ICT crimes are not considered real crime and that they will be paroled, or let out of jail for non-violent behaviour - therefore the deterrence is low
• one of the reason that American law enforcement officials tried to develop so much PR for the Kevin Mitnick case was so the public would know he got 5 years in jail and served 5 years
• see  http://en.wikipedia.org/wiki/Kevin_Mitnick