To its many critics, Dubai's economy is as artificial as Nakheel's islands. The emirate borrowed capital and labour to make speculative bets on real estate, of which The World is only one outlandish example. Now policymakers are scrambling to build an economic breakwater that might protect the emirate's prosperity from adverse tides: plunging property prices, ebbing trade and tourism, and the unaccustomed difficulty of refinancing its ambitions.