PORT-AU-PRINCE—Last January, hundreds of thousands of Haitians lost their lives and millions lost their homes in an earthquake that flattened much of the capital. A year later, Haitians appear to have lost something else: hope.

The impoverished Caribbean nation marks the anniversary of the Jan. 12, 2010, quake on Wednesday with little to cheer. Haiti's government, which itself was hit hard by the quake, has been incapable of responding to the crisis. Foreign aid has trickled in, and a rush of well-meaning charities have led...