ponzi schemes are pyramid schemes where you use the investments of future clients to pay dividends to existing clients, giving the illusion of "work" -- not sure how this applies to a service that actually does something for you
I think he may have been misusing the term, and simply trying to ask how they could possibly guarantee to provide that "for life", instead of "for however long the company still exists".
That being said, Ooma tends to sound terrible anyway.