That's a fallacy. The absence of bad news is not good news. You have to investigate other factors as well. Eg there is almost no incentive right now to do proper research. Thus it progresses slowly. Before full design documents have been published or reverse engineered, the security level is unknown.
I'll echo this. PPCoin has made sweeping changes to the Bitcoin protocol and it's hard to really tell what will work and won't work in the long run. One of the great things about Bitcoin was its simplicity in the protocol used to generate the network. However, with PPCoin, a number of complexities have been added and it's unknown how well they will pan out in the long term.
