Ponzi schemes are a little more subtle than pyramid schemes.

Investors are attracted via conventional methods. The schemer offers a reasonable guaranteed return on the investment, avoiding a "too good to be true" return. The return is paid directly from the funds collected by the initial investment-- but only for a time. The schemer eventually becomes a small dot on the horizon.

The Ponzi schemer aims to snare sensible, experienced investors, much like Scientology aims for dentists.

Sources: Kurt Vonnegut, Jr.'s Jailbird and an acquaintance of mine, currently living abroad under an assumed name. The bastard.