I am not a professional pilot, just a simple controller. Having watched this debate evolve I have a few thoughts to offer.
First, I feel for the crew - as has been pointed out, no one goes to work planning to make a serious error. I sincerely hope that they have had a fair hearing.
What matters now is that we - that is to say, everyone involved in this business - understand how an experienced and normally completely competent crew got suckered into making this error. By learning all of the lessons from this event hopefully other will see the holes in the cheese lining up in enough time to prevent a recurrence.
And without in any way pre-judging the proper investigation into the event I feel certain that every part of the system can make changes that can contribute to preventing recurrence.
As a controller I have worked at airports with similar traps and wouldn't like to guess at the number of times I've offered a brief comment to highlight a possible error being made. I've also worked at a very simple airport and had to prompt a few pilots to bear left a bit as they headed toward another airport about 15 miles away. My reason for mentioning this is not to point finger at pilots but rather to point out that we are all part of a 'team' with the same aim. And it wasn't all one-sided - there were a good few times when I issued a duff clearance and it was queried by the pilot just as I spotted my error, and a couple of times I'll admit when I hadn't spotted it. I was (and still am) grateful to the crews. In all these cases, one way or another, thanks were passed and I don't ever recall a hint of offence being taken on either side. And I could come up with a range of other similar examples where members of the 'team' contribute to doing aviation safely.
Trying to hang the problem on low experienced crew members (I only pick this example because it's higher up this page) or some other single factor is simplistic. More importantly it fails to take the opportunity to see every weakness in the system that contributed to the end result and so do what we can to fix them.