The general take away point shoud be that you check to make sure that the broker is registered with the offical financial and regulatory agencies in the country where it does business.
In the USA, this is the NFA and CTFC. In the UK it is the FSA. And so on.
Another interesting check that can be done for US based brokers is to see how much capital they currently have. If the broker is registered as a Futures Commission Merchants (FCM) you can perform a check on the
Commodity Futures Trading Commision's website for the broker's financial data
here. Just download the most recent .pdf or Excel file to see how much capital the broker has reported to the CFTC. Make sure to check out the Adjusted Net Capital, Net Capital Requirement and especially Excess Net Capital figures.