You can see what's on the screen in Farmville, but do the players understand the effects of periodicity and random reinforcement on the dopaminergic motivational system? The power of well-crafted images and sounds or emotionally manipulative language? Viral loops?
We in the industry know these things; for a layperson it's as obscure as the chemistry of physical addiction.
Arguably Diablo, WoW, etc. are all about pointless clicking for pointless reward.
Some people call it fun, some people call it manipulation. One has little farms and the other Sword of Wonder +101.
I guess the connection is, you buy some loot to get better at the game to play against random monsters to hopefully make some cash from the stuff you find.
Also, cigarrettes contribute to lung cancer, which kills thousands of people per year. Social games do not directly cause any significant social issues, and even if they may indirectly cause some problems, it won't be as serious as death.
We don't have to have games kill people to recognize that they are designed to manipulate and addict/engage its audience in a manner inimical to the interests of people.
Unfortunately, once we agree on the above points, we reach the real defense of social gaming, the slippery slope argument.
I believe that in due course of time, people will leave social games, after getting bored of them. The gaming market is not static.
At the same time that doesn't mean we stand back and let evolution go on its merry way. At the very least, we should be able to agree that there are some metrics we can analyze, perhaps the risk reward schedules and payout schemes, and compare them to their ability to create repeat behaviors/addiction in a percentage of the population.
(Heck even if we did wait for games to kill, we would have to work through the defence which will say: "well those people couldn't control themselves, so its just an outlier, or a freak case." )
Is A/B optimization in such a case thus an illegal/unethical experiment on human subjects without their informed consent? (Can Zynga 'Whales', that minority of their users contributing most of their revenues via payments of hundreds of dollars a month, actually give informed consent? Or are they on a binge?)
Tobacco companies lost giant class-action lawsuits because they (A) hid known harmful effects of their products; and (B) engineered their products to be more addictive. Could companies pushing gamification no matter the cost become the tobacco-company-pariahs of the mid-21st-century?