Mafia Wars

Zynga is the undisputed king of social gaming for Facebook and smartphones, and its stock price gives it a market cap nearly as big as video game leader Activision Blizzard. But at less than 5 years old, has the bulldog already jumped the shark?

Google views Web games as a key part of its strategy to take on Facebook. Instead of confronting its rival head on, Google is assembling building blocks -- such as email, music and games -- now and hoping to connect them later.

If you've been on Facebook for even a little while, you already know about the gifts. Every day, among the friend requests, quiz scores, updates and notes, there are usually a few random presents from your various Facebook pals. If you play "Mafia Wars," they may be things like a stabproof vest or...