Research by a "social game analysis firm,"—the existence of that title tells you a lot about the state of the business—indicates that 85 percent of social gamers, who began a new title sometime between July and September, quit playing it after just one day. Nine out of ten of them didn't play it after September.
Playnomics is the research firm, and the only good news it found is that if a player stuck with the game through a full week, a social game maker was more likely to make money off of them. Basically, the success of the product depends on creating an addict within the first day or two of the experience. I'm not sure cigarette makers performed that well.
There are a number of common-sense explanations for this. One is the vast marketplace of bullshit on Facebook and mobile platforms, in which cheap and insubstantial knockoffs count for much of the high churn rate, flinging mud on the more considerately designed games with higher production values and comparatively stable user bases. Another is that social gamers can quickly detect what is and what isn't appealing to them. Probably the biggest is that they run up against the paywall inside that first day and say to hell with it all.