More people stopped playing because they got bored. The fickleness of the public is the real danger in games like these, not the idealism of a few (which is a tragedy, as the latter would likely lead to much better games)

Is it really fickleness? Even hardcore games have a relatively short shelf-life. The only real exceptions are games like WoW which have been able to maintain some staying power.

For nearly everyone else all the money is made in the first few months after which it disappears into the bargain bin. It seems like social gaming is no different.

Longer-term successes do occur(Minecraft, the Sims, League of Legends are some of the biggest ones from the past decade or so) but the industry tends to quietly ignore them because they don't fit well into established models and formulas. The "blockbuster hit" model itself is a legacy of games being intertwined with the early-adopter consumer tech business, and has lately been challenged by an array of slower-growth stories that are essentially community-oriented service businesses.

You're talking about the wrong gaming space. You're talking PC. On the mobile side things are just as fickle (things go in and out of fashion,) but there are mainstream long-term successes: "Angry Birds" being the first among them.

OTOH, I genuinely stopped playing because of Zynga. Not out of some reflexive hatred, but because they started using push notifications to advertise upgrades/other games.

I don't really consider it fickleness when the casual game market is aimed at 'non hardcore gamers who want simple non challenging experiences that require no commitment and little depth' by definition.