1. Gambling in fact has many negative externalities. If someone gets addicted, the likelihood is much higher to be depressed. Depression is factor, which leads to high costs for the society.
2. Gambling addiction leads to economic costs because of crime actions. Other market actors have to increase their security standards, which means higher costs.
3. Many gambling addicts go as a consequence to jail. Jail means EXTREMELY high costs to society.
Definitely gambling got lots of externalities to our society from both gamblers and casinos end. Unfortunately most of the government are not having any kind of regulation to consider/take care of common people from those economic costs of gambling.