While Facebook has already communicated the elimination of bookmarks in the bottom bar and the addition of “Counters” next to each application listed in the left column navigation for bookmarked applications, the rules about how to use counters appears to be up to developer interpretation.
While you can’t see counters live yet, you CAN see how Zynga is planning to use it for Mafia Wars as their homepage has been redesigned to highlight a number of things and the counter-looking icon is in place in the upper right corner:
Besides Game News, the list of items includes Bookmark Me, Become a Fan, Join the Email List, and Social Job (where someone has responded to your request for help on a job). A user can hide them to reduce the counter down, but these straight forward tasks already created a counter with 13 items in it.
Initially, applications with high counters might get a user’s attention, but if these don’t provide value, they are likely to be ignored by users, much like the shotgun notifications were (several developers got in the habit of posting the same notification multiple days in a row). If instead, there are useful reminders, like when a crop is ready for harvesting or a energy pack is available, then users may find an enhanced utility around counters. Instead of having to police notifications, Facebook is probably hoping user reaction and market forces will ensure counters aren’t abused.
Much like email marketing (and notifications before), the key will be optimizing frequency and the message, mixing in marketing promos and game-specific activity. Given a core of notices with utility for the user, developers are also likely to benefit most in that users will actually be able to find their notices, which before were lost in a sea of messages in the old Notification tool.