Zynga may be a good business

More than 271m people play Zynga's games meanwhile once a month, and the firm said in March that it expects to make a profit this year of $630m on earnings of $1.8 billion. So its business is more real than those of some other online firms. Nevertheless it is not something a sober investor would bet the farm on. Users may tire of virtual vegetables and online Mafia Wars. Rivals are straining to grab Zynga's players. Electronic Arts, Playdom and Wooga have only about 30m monthly active users each, yet they may catch up.

What is more

What is more, Zynga depends on two other firms, Amazon and Facebook, like the cabbage crop depends on the rain. Even though it operates data centres of its own, it outsources much of its computing to Amazon Web Services, the cloud-computing arm of the online shopping giant. More importantly, most users play Zynga's games on Facebook. In September the social network pushed Zynga into using its virtual currency, called "Facebook Credits", so Facebook gets 30% of what Zynga's users spend.