Can we please stop using these terms interchangeably? They're totally different scams. The pyramid scam can be quasi-legal since it doesn't necessarily involve lying to the new members, just hoping they're gullible enough to think they are near the top of the pyramid. A ponzi scheme only has ONE person/group at the "top" and works by convincing members that the scam is a legitimate investment, and is definitely illegal.
TOTALLY DIFFERENT IDEAS