This is a pretty awesome idea! I think the ponzi scheme myth is a good one. I feel like when people say bitcoin is a ponzi scheme it just shows that they really don't know what bitcoin is and they also don't know what a ponzi scheme is lol... and too many people hold this irrational belief.
from what I heard, lots of people define a stuffs as a ponzi scheme if it satisfies this property
1) pay stuffs at low price
2) go home and wait
3) get more money later with what you bought earlier
Which covers pretty much every act of investment.
I see where you think it's similar. But when you buy some other 'investment' like a stock, there is something BEHIND that backing that. If you buy Disney stock, there is a company 'Disney' which the value in the stock is related. The stock cannot just go to 0 if people still believe in Disney, and Disney is still making money. Eventually most people will not believe Disney is worth the value in it's stock price - and sell it, and the stock will fall, but it won't fall forever, the value will reach a point where more people believe that Disney is worth more money than it's stock price, buy more of it, then it will rise. In a stable company, the price will rise and fall, but generally settle in an area.
Investing in bitcoin is investing in something that has no intrinsic value. Nothing is backing it. This is one part of a Ponzi Scheme.
The other part of the Ponzi Scheme is that people early in get bitcoins for free or with no real effort, and it's exponentially harder for anyone else to get them. Yes, people who were with Disney early get more stock options than those that come in later - but they don't get it for free. They worked hard - were usually underpaid for what they did, and did it for a long time before getting stock options. The stock options were their 'reward' for working so hard.
Another part of the Ponzi Scheme is that you need more people to join your cause to make it's value rise. And a cult-type following occurs. This is not true of a stock. Sure, the more people buy the stock, the more it might rise, but it can't rise just by people buying it, because at some point other people will sell when the value skyrockets too much, and the stock will stabilize. Lots of profits are made in stocks when a group of people buy a stock low, advertise it and pump it up like crazy (and lie about some 'secret' thing that they say will make the stock soar) until other people buy it based on their recommendations, and then the original people sell, and the newcomers are stuck with stock they paid too much for. This happens all the time, and is just as bad as a ponzi scheme, and is illegal.
So, yes, bitcoin has a lot in common with a ponzi scheme, but it doesn't necessarily make it one. If bitcoin eventually becomes a currency, the ponzi scheme aspects of it will be forgotten.