The block chain part just means a hacker just has to work a little harder to steal your bitcoins. The way I understand it, there are only so many bit coins, so the guy who started way back when with just enough bitcoins to buy a pizza, those same bitcoins are now worth a fortune, and the fortune grows as more people buy them and become worthless if people ever stop using them. It may not fit the exact definition of a Ponzi scheme, the the effects and characteristics are very similar. I still haven't heard the advantages unless you are a crook trying to hide your money dealings, a schiester trying to make a quick buck, or an anarchist who is confident, or possibly even hoping that our reliable 250 year old financial system is going to fail.