You mean keeping tabs on whether a person is trustworthy or not? Like you meet someone new, and through this ledger you know if he's a decent fellow or not?
It can't work long-term. The problem is
force majeure. Many people are trustworthy for years but they hit problems with personal circumstances, failed business, uninsured accident, ill health, and they default. At some level, even the TBTF banks can be "trusted" until an economic crisis when they become totally untrustworthy. Think of Lehman.
Trust-free money and math-based protocols are the only solution to sound money and stable macro-economics.
I don't doubt that it wouldn't have it's "defaulters", but I wouldn't like such a thing to be used only for financial purposes. I'd implement it (in part) the way the file system permissions in Unix style operating systems work: I trust Amy with my address information, Ishaq to come and browse in my shop, and the Water company to take up to $75 a quarter etc etc. And make it a kind of Diaspora style, personal server from which people can query information about you. Even if people abused the trust vested in them by others, at least we would have more information than we have right now about the kind of people we're dealing with. There are incredibly trustworthy people who, instead of getting the maximum opportunity to utilise it to the benefit of others, have it used against them instead. The trust abusers disappear off to a place where their relative trustworthiness has higher value, and their trust stock is largely undamaged. Everyone loses really, I'd argue that even the abuser does unless they're a completely remorseless psychopath (an information tool to weed those out before they go on to commit major fraud or murder? Sounds useful). And the abused feel like they can't trust anyone in general.
It just seems to me that we have the ability to create some kind of information system, based around trust itself, the world has too many people in it to have to constantly assess people for who they really are. If bad trust credentials followed you around everywhere, is that not a good motivation to always
try and behave with good intentions? The difficulty I think is: what is the measure, what is a unit of trust? I have no answer to that, or at least not now. I trust some people more or less about different things, but how do you reflect that objectively?