Btc is NOT a ponzi scheme and anyone who calls it one either doesn't understand what a ponzi scheme actually is or doesn't understand btc - likely both. Btc MIGHT be a pyramid scheme - that is at least worth discussing, but not ponzi.
Please describe
how BTC might be a pyramid scheme... I'm interested in this.
When the price of bitcoin is bubbling (as it was the past couple months), people buy bitcoins because they hope to sell it tomorrow for more money. This continues until there are no new people to buy the bitcoins at a higher rate, and the price collapses.
However, when the price is more stable (like for most of 2012), bitcoins are able to function more like a currency. People sell things for bitcoin and then use the bitcoins to buy other stuff.
So if you are not using bitcoins as a currency, then it resembles a pyramid scheme. Bitcoin is very flexible, it has many uses and each person can chose whether they want to view it as money or a commodity, currency or investment, store of wealth or payment processor.