I attended a presentation last week at CSIRO on honey and mead. It was quite an interesting event with some inflammatory topics covered, like honey toxicity from Pattersons Curse.
This weed, which is a prolific nectar producer, contains a liver toxin that can be transferred from both pollen and nectar and over-consumption can be fatal. It is however only a small contributor to our honey production so is unlikely to be an issue.
The other major topic covered was botulism in honey. All honey contains a small amount of botulism, and as a result honey should not be fed to children under 1 as their immune systems are unable to deal with even this small level of the toxin.