I didn't even consider looking at Ethereum (despite having heard about them), but now I will take a peak at them, what you are writing is just what I was looking for for my own projects. Thank you.
As I understand it, it's like Bitcoin except that you can add arbitrarily complex (turing complete) rules to addresses. So you could write things like "each time there's a deposit to this address, split it between all the previous depositors to this address in proportion to the site of their deposit, until they have received 150% of the amount of their deposit back" into the blockchain. Then everyone can see the rule and be sure that the Ponzi was "fair".
Obviously it's still a Ponzi, and some people are going to end up out of pocket, but at least there's no OP taking his 1%, and there's no risk that OP will run off, because he never gets access to the coins.