Basics of the scam: Deposit in Dwolla, buy Bitcoins on an exchange, send bitcoins to your own wallet, chargeback Dwolla deposit.
A couple of months ago TradeHill, the second largest bitcoin exchange, discovered Dwolla billed them $30K in chargebacks despite their claims of never doing that.
It's this Dwolla issue that stopped the influx of new money into Bitcoin and now the price is 90% down.
This is a key problem for growing any kind of digital cash like economy: somebody needs to take the risk of turning chargeback-money (USD) into cash-like money (bitcoin), or you need to have a network to somehow take physical cash.
It just illustrate that online transactions should be chargeback-able to protect consumers from fraud. Bitcoin just doesn't cut it.
I believe there's a place for non-chargeback online transactions. Just as there's a place for non-chargeback in-person transactions (i.e. CASH).