Slashdot links to some articles about online reputation systems.
Apparently, many of the commenters assume that implementing something with a new set of hardware will force us to reinvent it. Thus this:
I'll play devil's advocate here...
Let's say you comment on the theory concerning the use of demolition explosives on one of the world trade centers - pointing out that the collapse of the WTC doesn't look like other building demolitions [google.ca], or that the "symettric demolition" claim is incorrect.
However, the conspiracy theorists on the site are extremely fanatic about their theory (as opposed to a more moderate site that tries to investigate properly.) As a result, you receive a large quantity of negative feedback that attaches itself to your online reputation.
Other things that can affect you would be playing RTCW:ET, where you get kicked from a server for n00bism as you didn't dodge the three panzers that get fired into your local area (because another player thought you should have.)
And my personal favourite - just claim you support Bush. Your reputation would instantly tank.
Right. Interesting. But there isn't a single argument here that doesn't apply to real-world reputations. Nobody claims that "We shouldn't have a thing called 'reputation', because paleocons will think Daniel Larison is swell, but atheists won't like him a bit. Thus reputation, which we're treating as a scalar, is bunk."[1]
The Right Question
The problem is, of course, that reputation isn't so simple. The Reputation Question is not "What is Byrne Hobart's reputation," but "What is Byrne Hobart's reputation in the field in which I'm interested, according to people whom I find reliable?" To make it easier, consider a controversial but well-known figure, evaluated by a couple hypothetical (read: highly stereotyped) third parties. Let's ask a 20-year-old college student and a 40-year-old linguistics professor to evaluate Noam Chomsky's reliability in terms of 1) foreign policy, and 2) linguistics. For simplicity's sake, they can give us one number, ranging from 0 to 1, that represents the correlation between what Chomsky says and what (given enough time) they'd expect to be true.
The 20-year-old undergraduate knows that Chomsky was against the Vietnam War about six years before we withdrew and opposed to intervention in Iraq before we even got there. The undergraduate [2] sees this as sufficient evidence to rate chomsky as about 95% right on foreign policy. Unfortunately, our undergrad isn't aware that Noam's reputation stems mostly from his early academic work; he gives Chomsky a 60% chance of being right about linguistics. Our professor, on the other hand, reverses these measures: Noam wrote one of the most influential linguistics texts, and his political views -- while cogently articulated -- sound more contrarian than consistent.
When we can ask (what skeptics consider) the same question ("What is his reputation?") and get four answers from two people, the problem is probably the question itself. The right question requires a chain of trust: A, whom I consider 90% reliable, says that B is 80% trustworthy, while B notes that C is about 70% accurate when making guesses about future oil prices. Thus, the correlation between price changes and C's predictions should be about .90 * .80 *.70, or around .5.
I concede that the main conclusion is that when you really think about it, trust is boring.
The Right Person
What's more interesting is whom to trust: websites like Slashdot and Wikipedia use a sort of gift culture, in which people write for free and are judged based on the quality of their writing. But reputation -- as, for example, someone with unconventional views backed by clever research -- doesn't always tranfer to other sites -- where the same iconoclast might be seen as a time-wasting troll. It's trivially easy to register a reputable name on a new site (unless your name is 'cmdrtaco'), so names themselves don't mean much.
But commercial websites don't have this problem -- they authenticate a user's identity by using a unique identifier that the user carries with them almost all the time. There's probably a framing issue, here: once people know they're going to spend money, they assume that the company they're spending it on won't accidentally share their credit card information. And because losing a credit card is so inconvenient, users hang on to this new identity. Rather than waste money and time building a new reputation system they use one that's already in place -- and instead of a nebulous reward like 'consistency', users can have an ID that's as synonymous with them as their bank account.
Security is an obvious concern, but commercial sites have been working on this long enough to have it nailed: instead of forcing people to transmit their full credit card numbers, all we really need is a one-way hash of some or all of it. So rather than log on to one site to check your email with one ID, and another site to comment on a blog with another ID, and yet another site to buy a book with yet another ID, you'd perform one log on (matching your name to a hash output from your credit card number) and the central ID database would take care of the rest.
Just In Case
If you really, really want to link a person's identity to a single number that represents just how much they ought to be trusted, I can think of one tricky but viable solution: prediction markets.
[1] I'm only using this example because I like Dawkins and Larison -- they're both reputable, as far as I'm concerned -- but they each probably consider the other a confused and conniving dissembler.
[2] Whom we stipulate reads Counterpunch and smells vaguely of fennel.