Passive Facebook gamers like this writer had been in and out of virtual farms, cafes, mafia fiefdoms, and embellished two pets with fabulous lifestyles to be envied.

Sustaining the interest of such passive gamers, who only tries to pass the time and all of a sudden be muddled in some other work load and day-to-day existence, is the source of a major concern for online game creator Zynga (Nasdaq:ZNGA).

Struggling to prop up its finances since its IPO, Zynga closed down ineffective games that does not help re-coup losses and could even save in terms of domain allocation and production.

In spite its reported 1 million active users world-wide, Zynga closed down on Sunday Petville, which has been rivalling another product Pet Society. Pet Society, on the other hand, has similar mechanics as having a virtual pet but has about 5.6 million users globally.

Zynga also shut down Mafia Wars 2 with only 200,000 monthly users, which is not as successful as its predecessor Mafia Wars, but its popularity is also fading rapidly.

Other game apps on Facebook that has been closed down in December and November include Forestville, Fishville, Indiana Jones Adventure World, Mafia Wars Shakedown, Montopia, Mojitomo, Vampire Wars, Treasure Isle and the World Scramble Challenge.

Gaming analysts said aside from the quandary as to how to sustain visits from online passive gamers and users of Facebook, Zynga has sustained some financial blows when its exclusivity agreement with Facebook has been abolished in October. Although it can now sell its games to other social media outlets, this has not been turned into profits for the company.