I'm not trying to be chicken little about it, it's just above my personal risk tolerance.
I've seen ratios that ~20% of the FX market is retail speculators; I'm not sure whether that's volume or trades, or both. But the idea that 20% of a market is actually 0.1% (removing the leverage), means that if you sucked out the leverage the market would change drastically.
I'm happy the Swiss currency popped like that, because it shook out some of the less-capitalized brokers, and slapped the hands of others that dabbled in it but hadn't experienced a loss. Even IB lost 2.5% of their assets, and they have the least amount of leverage of most US providers, which have less than 1/4 the leverage of most British brokers, which have less than 1/5 the leverage of Qatari brokers.
IB 40:1 (non exotics)
London 200:1 - 500:1
Asia (200:1-800:1)
Qatar (500:1-1000:1)
It all might work out in the end, and hopefully regulation (both government and broker imposed) can reign it in before it becomes systemically risky. But in the mean time it's just too much for me to wrap my head around.