Brendan Sinclair for Gamesindustry.biz:

Audience management firm Playnomics has released a report on user engagement for social games it tracks, and the findings show that players aren’t exactly patient in giving free-to-play titles time to hook them. The group found that from July through September, roughly 85 percent of new players in the US never went back to their games after the first day. And of those who joined in the first part of that stretch, 95 percent had become inactive by the end of September.

Unfortunately, most of the time with free-to-play games, you get what you pay for.