It really is a shame people have lost really large chunks of cash on this. But I just don't see how most people can hope to claim the money back.
If you had a guaranteed stop, and the terms of agreement say that stop will be honoured, you have a case. I am sure a lot of the spread betters will be updating their terms to something more akin to 'best efforts' rather than guaranteed stops.
If on the other hand your point is that it moved more than you expected and you can't pay, well unlucky.
Screenshots of a market data system showing particular levels tell you nothing. In a normal market, if a particular level is trading, you can usually reasonably expect to be able to trade at or very near that level.
However in this case, there simply wasn't a market. Even if, say, EUR 1 mio traded at 1.1950, that doesn't mean there was the liquidity to trade 10 or 20 mio EUR. The next price was 1.10. Then 1.05. Etc. That is the nature of these things when you get so far out of range. Saying "it traded at 1.1950 so they could have cut me out" is idiotic and shows no understanding of the nature of the market in that half hour.
If you had it the right way round, you'd expect whichever spread better or broker to pay you your profit, so why should you not pay your loss? (Again with the caveat above regarding guaranteed stops).
I am not a wheeler dealer. I have a relatively small stake in my trades because it is a pastime for me- I have enough common sense to know what the markets are like and take my chances with Black Swans. I was not trading forex at the time and I feel sorry for those who lost money but, in all honesty, I cannot blame the SCB for looking after their own interests. They had a strong currency and were tied to one that may take drastic measures this week with QE. What choice did they have? Frankly, I would have done the same in the same position.
I remember the crash of 1987. I had options, then, and my broker would not pick up the phone. What did I do? Goodbye, option trading! Brokers are no different to SB firms when the stakes are down, believe me.