What's happening to honey bees in the US?

In case you were wondering why the bee population in the US is suddenly in decline, check out this PLoS Biology paper that describes the problem and lists a bunch of possible reasons. It seems that the specific issue is a drastic reduction in adult workers, called CCD (colony collapse disorder):

"The syndrome is mysterious in that the main symptom is simply a low number of adult bees in the hive. (This is a bit like going to a previously well-populated hen house and finding hardly any hens.) There are no bodies, and although there are often many disease organisms present, no outward signs of disease, pests, or parasites exist. Often there is still food in the hive, and immature bees (brood) are present. The cause of the loss of bees seems to be the sudden early death, in the field, of large numbers of adult workers [2]. Curiously, the dead colonies tend to be left alone by the two cleptoparasites that normally infest dead honey bee colonies: the wax moth Gallaria mellonella and the small hive beetle Aethina tumida. Could this be due to some toxic residue in the dead colonies? Perhaps this was a contributing factor, but more likely the time of year meant that there were few cleptoparasites about—their abundance is seasonal."