A colleague passed on a three-way e-mail exchange discussing the difference between hang and hung. By itself, that isn't all that interesting. The usage guides all give more or less the same instructions. This explanation from The American Heritage Dictionary is typical:

Hanged, as a past tense and a past participle of hang, is used in the sense of "to put to death by hanging," as in Frontier courts hanged many a prisoner after a summary trial. A majority of the Usage Panel objects to hung used in this sense. In all other senses of the word, hung is the preferred form as past tense and past participle, as in I hung my child's picture above my desk.

What caught my attention was a remark by one of the participants that the use of hanged seemed to him much less acceptable when in the active voice than in the passive. In other words, to this speaker, Saddam was hanged by an unruly mob. [passive] sounds much better than An unruly mob hanged Saddam. [active] He went so far as to express the opinion that "almost nobody" uses the active construction. Since I don't share that intuition, I ran a simple search with Google: Searching for {"they hung him"} gives 44,900 g-hits. Searching for {"they hanged him"} yields 25,300 g-hits. At first glance this looks like some support for this person's intuition. But if you ckeck the results for {"they hung him"}, you'll see that many of these expressions do not involve hanging by the neck. A lot of these hits, in fact, refer to the spiritual "They Hung Him on a Cross". Sure, that sort of suspension ends in death, but "they hanged him on a cross" would misrepresent the form of Jesus' execution. Searching for {"they hung him" -"on a cross"} gives only 27,100 g-hits, almost equal to the count for {"they hanged him"}. And a quick glance at the remaining results suggests that many of these also refer to something other than hanging as execution. So at best, the two usages are split. But why does this person find the active form weird? I suspect that for him, hang, when it means "execution by hanging" is an irregular verb with a different paradigm than hang in its other senses. Hang = "to execute by hanging" is formed (by the prescriptive rule) as a regular verb. That means the preterit (i.e., the form used for the past tense) and past participles are both formed with -ed: present: hang preterit: hanged past participle: hanged Hang in its other senses is an irregular verb with identical (non -ed) preterit and past participial forms: hang/hung/hung. Note, however, that plenty of irregular verbs have different forms for all three (e.g., swim/swam/swum). Now the key point here, and the reason I've digressed into verb paradigms, is that the active form of a past-tense clause uses the preterit, while the passive form uses to be as an auxiliary and the past participle. You can see this difference intuitively if you contrast active and passive forms of a sentence using one of the verbs with distinct preterit and past participial forms: Jake rode the horse past the judges. [active--preterit] The horse was ridden past the judges. [passive--past participle] If this person's mental lexicon has hang (execute) as an irregular verb with the following paradigm: present: hang preterit: hung past participle: hanged his aversion for 'hanged' in the active would be explained. That would be a somewhat unusual pattern: an irregular preterit and a regular past participle, but I don't see any reason why it's impossible. One parallel that leaps to mind immediately is the common American pattern for dive: dive/dove/dived. It would be interesting to know how wide-spread this distinction is. Unfortunately, I cannot thing of a simply way to use Google to check for it.