You lose all your money when you can't close your bet. This happens when there is no market. For example, the price of oil went negative. In that situation, you are still liable for the continued loss even though you cannot not close the bet. As soon as the market is available again, the bookies closes it and leaving you a negative balance that you have to pay off.
That would come under "being daft"! If you didn't use a cfd account, you'd just hang on to your oil shares. True it could take a while. Not that I'm sure - commodities don't usually go negative!
Dear reader - Contracts For Difference are where you only put up say £100, but at 20:1, then you profit from the price difference on your 2000, £1 shares, over time. If they do 2.2x in price, you win the (2000 x 2.2-1) = £1400.
If they go down to half though, tough, you lose 2000 x (1-0.5) = a grand. Plus fees. You're wiped out. So don't do it!
And well yes, if you dabble in a currency which is about to go obsolete then.... I dunno, I wouldn't try!
There ARE other things which can go wrong, like a "position" becoming illiquid or the broker going bust.
The FSCS does enforce rules and (untested afaik) offer a guarantee up to 85k.
Also, it's illegal for a trader to have a claim on you other than the deposit you make.
So you could, in theory, open a new account, dabble a bit to get respect, so they offer you bigger ratios (30:1 is easy, 500:1 possible), then make a big punt on one position.
If you win then great you multiplied your money. If you lose, you lose your pot, and they can't chase you to pay the extra 29/30th or whatever loss.
So you do it again until you win. There are loads of platforms, if they kick you out. If you win more than once in 14 or whatever, you're winning.
Yeah I checked wheat. It went up 60% or so? Definitely scope, but hardly a secret!
By the way, Tesla dropped 10% or so today. "Everyone " knew it was likely last night, so many like me dumped it. What odds would you give that it'll bounce back, though? Buy the dip!!