I think it would be a straight numbers decision as you guess. A lot of companies would worry about how this would impact those high value and long term customers and how it could effect retention in other games and future projects. I think Zynga is passed that point now though (if that ever was a concern for them, they have never really been a games company a rational person would have a strong connection to).
Pretty much all the big name MMOs released in the past 10 years have gracefully downsized and maintained maintenance for the player base.
Pretty much all the big name MMOs released in the past 10 years have gracefully downsized and maintained maintenance for the player base.