My primary concern with ripple is exactly what TradeFortress has just demonstrated. Ripple IOUs have different values based on the issuer. If they traded on an open market, you would see this. IOUs for a trusted institution are worth more than IOUs for a less trusted one. E.g. you might see Bitstamp USD IOUs trading against Weexchange IOUs at a non-1 rate, such as 1.1.
But we don't see that in ripple (as far as I can tell). Instead, we see a markets labelled by the currencies only, such as USD/XRP. But whose USD? Where's the Bitstamp USD / Weexchange USD market?
The fact that default risk fluctuates is acknowledged by participants in the real financial markets. We have credit markets. The values of various entities' credit float against one another. They are not all the same.
These are legitimate concerns and questions, however what TradeFortress did does not illustrate your concerns, it merely shows that he can use technology that newbies don't understand to facilitate a fraud. At this point in the Ripple system you don't trust any issuer of USD that you don't trust equally with another issuer. You may not like it, but that's how it works right now. He is taking advantage of ignorance, while simultaneously misleading through half truths and lies. Read his post on the Newbie board if you're unclear on this.
He said he was going to deposit 1 BTC in to a person's Ripple account. A newbie who barely understands Bitcoin is not going to understand that in a completely different system (Ripple) that BTC is an IOU. Then add an additional layer of complication in that most people are not used to being in control of who they trust when it comes to money IOU's (government usually is) and you have a recipe for theft that is unnecessary and proves nothing but that Tradefortress is willing to hurt people in order to take down Ripple.
The worst part about it is he has credibility on this board and so newbies are liable to trust him (Luckily a moderator put warnings on his OP, since all warnings by other people were self-moderated by Tradefortress). Abusing this trust and not having moderators put a REAL stop to it - This is just plain wrong.