still brittle since it depends on active & hover classes, but removing those dependencies should be trivial

better.greedy.droppables.js

$("#element").droppable({
  tolerance: 'pointer',
  activeClass: 'ui-state-active',
  hoverClass: 'ui-state-hover',
  drop: function(evt, ui) {
    console.log('dropped',evt,ui)
  }
});

$('.ui-droppable').live('dropover dropout',function(evt,ui){
  //var scope = $(this).droppable('option','scope') // TODO: watch for scope
  $('.ui-droppable').droppable('enable')
  $('.ui-state-hover').not($('.ui-state-hover').last()).droppable('disable')
}).live('drop',function(evt,ui){
  $('.ui-droppable').droppable('enable')
  $('.ui-droppable').removeClass('ui-state-hover ui-state-active')
})