For many people, the problem is they are owed by some huge corporations, it's not like when it comes to debts your friend is exactly more credible than some huge corporations. Also, if the debts can only be exchanged between friends, why not just go buying bitcoins from them with cash/bank transfer?(especially the assumption here is you already trust them)
The first line reads like an insult to a lot of people's friends. I'd trust my friends more than anyone or -thing I don't know as well, including but not limited to corporations.
I think it's important to formalize trust. Just because there exists some complicated transaction using firends' trust, few would execute it by hand. If ZeroReserve manages to simplify this process enough, it becomes preferable to trusting an ominous entity that tends to eat your funds in one big bite -- like Gox and the numerous other failed exchanges.
Banking -- the trade with IOUs -- is actually quite efficient. It mostly fails on the wrong places piling up trust. If trust becomes more explicit and less reliant on magic entities doing magic things with trust they implicitly get, it's a great approach.