Farmville, Top Facebook Games Continue To Shed Users

Never played Farmville, but I'm guessing part of the stickiness of the game was the slight but not insignificant emotional pressure of seeing "<your friend> wants you to plough him/her" or whatever the notifications Farmville sends out actually looks like. :p Without that slight pressure of seeing your friend asking you for help or collaboration or whatever, it's probably become much easier for people to not play that game.

When these articles say "losing millions of users" they mean losing millions of active users, which in the case of Facebook is the sum of all new and returning users over a given time period.

They're not talking about registered users.

Losing notifications hurts both your new user growthand your retention, so you see a reduction in active users. It remains to be seen whether these apps are just settling to a new plateu of activity or if they're actually dying.

I would say some of these games have a very high turnover rate and relies on constant recruiting of new players.

With just regular players quitting and less options available for hooking new ones, the net total is that they are losing out.