Like a lot of people I've been playing Mafia Wars on Facebook for quite some time. You can usually check your progress once or twice a day, which probably takes a couple of minutes at a time.
Yes - it is addictive
No - Nobody will ever win.
But it's still semi-amusing and keeps me vaguely entertained.
However they may have gone a little bit too far now with their latest addition - SMS notifications.
If you are a player based in the US you will be able to signup to get alerts when you are attacked etc., which means that you will never really have any peace from the game, which I don't think is a particularly good idea for the players. For Zynga, of course, the more time people spend on their platform the more money they will earn.
Here's what the offer looks like: