Wow, this is an interesting thread!
More so for me, as I've only just been introduced to the idea of Black Friday. We don't really have anything like that over here. Sure, there's Boxing Day, but I've never seen hordes of people outside stores - mainly because they're probably sleeping off Christmas night!
I find it difficult to believe that an incident like this wasn't foreseen. Not necessarily with such tragic results, but when any large crowd gets together, they're going to be uncontrollable (especially if they've spent hours standing/sitting around in the cold). Black Friday is a known event - it's not as though this was the first year it's taken place.
I can't really comment on how much security this particular Wal-Mart hired for Black Friday; whether they hired more than they would normally. One would hope so, as they naturally would expect more shoppers than on a normal, working day.
As someone said, these events tend to disappear from the news after a while, so any incidents in previous years that perhaps didn't result in injury, but potentially could have done either didn't make it to the public domain, or stay in it very long - so people not directly involved don't remember.
I think that perhaps in light of this event (and any others that haven't been reported), some sort of ticketing system, where tickets are issued on a "first come, first served" basis (if people are going to camp out for hours, then why shouldn't they be rewarded with first entry, as opposed to people who turn up just before the doors open who may get in before them) and the crowd is let in in groups of say, 50 people every minute. That way there is some semblence of control to the entry.
Of course, that relies on people respecting that, and whether they would or not is another question.
With regards to who is responsible, I will say that a manager is responsible for the safety of his staff, as well as for turning a profit. Not having a safe work environment for staff means walk-outs, and yes, I'm sure more staff could easily be hired, but there are the logistics involved. I'm sure that a risk assessment meeting would have been held before the Black Friday sale. Obviously the risks were underestimated. I doubt they will be again. The Western World has gone Health and Safety-mad, especially with the increasingly litigious mindset of the public, both in the United States (which is, of course, famous for it) and also now in Europe. I'm not saying that it is not a bad thing that Health and Safety is a main priority: of course it is. But perhaps some of the more "ridiculous" laws have lead to Health and Safety being thought of as voluntary as opposed to compulsory.
Of course, this is all speculation with regards this incident, as all the "facts" that have been reported may only be two-thirds true, or mis-reported, and I doubt the entire truth will come out until a court case. (I say this with experience of first-hand knowledge of incidents reported in the press where the facts are either mis-quoted or in fact entirely made up of a mish-mash of truth and fantasy.)
As for unions - I wrote a bit about them in the union thread.
Here is my post (assuming I linked to it correctly!)
Apologies if this doesn't make much sense: I'm writing it at 1:30 in the morning. (Perhaps I should also state that everything I've written is solely my opinion!)
[Edited to tidy up the wording and fix links.]