Interesting, I don't understand how this should be worrisome - the receiver has to know what kind of transaction he is engaged in. Sending BTC which is not redeemable is the same as sending no money at all. It is exactly analogous to signing a contract. If you don't understand the terms you shouldn't sign it. So a sender might trick the receiver into believing that the contract does something he didn't know. But if you have a network of trust you hope that the sender gets punished for this behavior. Most of these issues haven't been solved yet, but it's a bit like saying the internet is worrisome because its peer to peer. I mean its exactly this part that is the most fascinating about the network. Sending from A to B we can already do with paypal.