Social Games Are a Constant Deployment Environment
You're releasing constantly, and with every new version you can be absolutely sure that 100% your users are working on the same version of the software. You can even release a games "sequel" simply as another update.
For developers who are coming from the web side this may seem like business as usual, but for those of us coming from "traditional" game development this is a fundamental shift. And at first it seems like a dream come true, but there also isn't a developer I'm speaking with who doesn't have a list of fixes, updates, and features that's far, far out ahead of the actual production time that they have to do the work in.