When BFL first opened up their Monarch refunds, the reason that they publicly gave for why there was a sixty-day delay on refunds is because they had to sell your place in line to another customer. Using a later customer's money to fund the payout of an earlier customer is practically the definition of a Ponzi scheme. That's why I made the comparison.
A company not providing or delaying refunds doesn't make them a ponzi, no matter the reason they state. More then likely their refund policy's objective was to deter people from requesting refunds. Remember, the people buying Monarchs were buying a pre-order for a piece of equipment, not an "investment" that provided returns similar BT or any ponzi scheme.
BFL is at best a mismanaged company and at worst a total scam, but I don't see how they could be considered a ponzi, especially not an obvious one.