WAIT - Bitcoin is a Ponzi Scheme !!!
* joking *
If you trade another commodity for bitcoins and SAVE the bitcoins, they you are gambling on relative future demand versus todays demand. If the future demand for bitcoins is higher you win, if it is lower you lose.
There are only two reasons for other people to "demand" bitcoins. Either they wish to save them for future use. Or they wish to trade them in the near term for another commodity.
So if it turns out that "all of the demand" for bitcoins is because people want to save them and sell them later when they are in higher demand, then you have a classic ponzi scheme.
If "all of the demand" is for use in immediate trading, then you have a very high velocity type of currency. (Changes hands many times over a short period of time) Counter-intuitively this "highest velocity" case actually defines the minimum demand for currency in a given community.
So yes, at the moment bitcoins as an investment fit nicely under the umbrella class of "Ponzi scheme". As a holder of bitcoins, the value of the coins increases
most as more people decide to purchase bitcoins and save them.
When trading, the highest demand for bitcoins is caused by the smallest cycles.
1) A has bitcoins, wants Apples; B has Apples, wants bitcoins
2) A has Dollars, wants Apples; B has Apples, wants bitcoins; C has bitcoins, wants Dollars.
3) A has Dollars, wants Apples; B hash Apples, wants Oranges; C has oranges, wants bitcoins; D has bitcoins, wants Dollars.
In (1) trading one unit of Apples, requires one unit of bitcoins
In (2) trading two units (Apples & Dollars), required only one unit of bitcoins.
In (3) trading three units (Apples, Oranges & Dollars), required only one unit of bitcoins.
So as bitcoin becomes popular for people to both buy and sell things using bitcoins, the demand for coins could very well drop. If you are speculating in bitcoins but promoting bitcoins for trading, you want small cycle trades (a la paypal). Large cycle trades minimizes the demand for your holdings.
So I really wasn't blowing smoke when I said Bitcoin has many Ponzi like characteristics. That may not be the intent of bitcoin users, but neither was it the intent of Ponzi's investors either.