You are correct that these types of failure can occur in all types of firearms Unfortunately not all failures can be attributed to ammo alone! There are a number of reasons for a pistol to have a catastrophic failure, such as pulling the trigger when the barrel is clogged, over-charged cartridge, under-charged cartridge, weak brass, metallurgic failure, insufficiently supported case etc.
I will disagree with you about the results of a case head rupture. The light damage you suggest can and does occur but other damage can occur as well. some of the damage done by the rupture of a case can be blow the magazine out of the gun, damage to the locking block or engagement surfaces, damage the trigger, ruin the trigger bar, rupture the barrel, peel the forward edge of the slide at the ejection port up, and do other nasty things. In general, glocks tend to contain case failures fairly well, but under some circumstances they can cause injury as well as damage to one's gun. I for one would prefer a better supported case as opposed to a lesser supported one.
The following statements can be found in Accurate Arms' current reloading guide regarding .40 S&W pistols and supported/unsupported cases:
"In recent years it has become very apparent that there exists a situation regarding some pistols chambered for the .40 S&W cartridge. Some of the pistols currently available to shooters may not provide complete support to the case when a cartridge is chambered."
"This information [AA's load data] is safe for use in firearms which provide complete support of the case. Failure to fully support the case with cartridges of such intensity may result in bulged cases, ruptured cases, separated case heads or other consequences which may result in damage to the firearm and/or injury or death to the shooter and/or bystanders."
"If you own a firearm chambered for the .40 S&W, we recommend you contact the manufacturer to determine if the case is fully supported."
"If your firearm does not provide complete support for the case, DO NOT USE Accurate Arms Company data or products to reload your .40S&W ammunition."
"This is the first time Accurate Arms Company has felt it necessary to place such a restriction on the use of our products, but the continued safety and welfare of the shooting public compels us to do so."
NOTE THIS IS NOT DIRECTED TOWARD GLOCK(my statement) I feel that you might be perceiving this as a blanket attack on the glock, it is not intended to be, I just have some reservations about some design decisions that they made earlier on in their .45 and .40 cal line. As I have stated before I believe they have corrected the situation in current production. This kind of occurrence can and has happened to other companies. I also feel that glock could have handled it in a better way but they were probably doing it the way their lawyers told them to.
I don't usually like to beat a dead horse too much, but in this case I can't resist.
Accurate Arms came out with that disclaimer when people started blowing up 40 cal. pistol using AA#5 trying to hotrod the already hot 40S&W. SAAMI pressure rating for it is 35,000psi. What AA did there was basically say that any blowups in ANY pistol were not their problem as MOST pistol do not have fully supported chambers. H&K being one of the few exceptions.
As to Glock changing their barrels, I can tell you first hand that my G21, which is only two years old, leaves a whole lot of case hanging out in the air over the feedramp. Never had a problem with it. Of course, the 45ACP is a lower pressure round than the 40.
As to your comments about case failures and what they can cause, we will have to disagree. Common sense should tell anyone that if a case fails, pressure is immediately released down the mag well. No barrel splitting could occur from that. An obstruction would cause a split barrel, as you said. As could a double charge of fast powder. But is a case of severe over pressure, not a lack of support in the chamber.