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." )
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.