Random, in fact any, shoe screening is a health hazard. Why should I have to walk across a floor in my socks that is A) contaminated by the dirt from everyone elses shoes, and B) is not disinfected?
Frankly I think you are being a bit paranoid. I've been flying twice weekly for the best part of 8 months now, and the shoe business has been going on for most of it. I don't appear to have caught any nasty diseases as a result, nor do I think anyone else will.
It is inconvenient, yes, but I actually find it more inconvenient getting my laptop out of my bag, or having a pile of about 4 trays to screen (hence why I suggested replacing the trays with plastic bags).
And
AFAIK it is only done because the bottom couple of inches of the screening macjines doesn't do any screening. So why not put a small ramp in the arch that you can stand on?
Metal detectors, which is what the "offending" detectors are at least in the UK and Europe where the "blow" type machines are pretty much unknown, do not detect explosives, wherever on/in the body they may be concealed. They detect metal. The shoe carnival isn't intended to stop people putting knives in shoes, else they probably would do what you suggest. It's to stop people putting explosives in them.
It is worth noting that (before this all started) I used to have a pair of hiking shoes which had metal framework in the sole. They'd alarm so often that I just ended up putting them straight on the belt to avoid the hassle. Thus, some metal detectors *do* detect metal at the bottom. But that's not the point.
I thought the whole point of locked cockpit doors was to deny control of the aircraft to anyone who posessed any weapons and threatened the cabin crew. Does this mean that cockpit doors are not as safe as advertised?
Unless planes were built whereby there was no physical access from the cockpit to the cabin, which might itself be a safety issue in terms of what happens if the pilot/copilot became ill or needed for some reason to check something out in the cabin, the door is only as strong as the human with the code/key to access it, or to influence its access. Thus, even if it were 6" thick steel with 10 locks, 5 keys going to the cabin crew and 5 to random passengers/air marshals/whatever, there may still be a way to get in.
Thus, in that sense, they are indeed not impenetrable. I don't think anyone's advertised that they were; they are just more secure than the old type which could easily be kicked in by one not particularly large person.