My 18-year-old brother, just about to start college, can’t get a credit card to save his life. He doesn’t have bad credit, but he’s never had any account in his own name, and, in this economy, no bank wants to take a risk.

College freshmen may have no financial records, but, in an age of Twitter, Facebook and other social media, most undergraduates have established online “paper” trails that will follow them for the rest of their lives.

College students are cautioned that all online activity creates a permanent record. A photo taken in a moment of drunkenness could be the first hit when someone Googles your name. The rule is: Don’t put online anything that you wouldn’t want an employer or a parent to see, because everything on the Internet is public. This is broadly true and important to consider, but, as more of our lives move online, it will not be the most pressing concern.

The Faceboook photo problem ignores the power of data in the aggregate. The risk isn’t of being misrepresented by a single anomalous picture or comment, but of being classified based on accumulated photos, comments and blog posts. The same data-mining techniques used by financial firms to condense all of a person’s financial transactions, bank account statements and purchasing habits into a credit score can be used to discern patterns in our online behavior and quantify it.

Think of the distillation of your online habits as a kind of reputational credit score, analogous to the reliability ratings provided on Web sites like eBay. Employers, friends and prospective dates could filter your activities to try to gauge your character. By making data freely available, our generation is building the foundation for a kind of reputational economy, where the coin of the realm is trust from a peer group.

The reputational economy doesn’t exist on a grand scale yet, but individual Web sites are starting to utilize user data to assign reputational worth to users and award privileges accordingly. At the end of August, Wikipedia established new guidelines for “the free encyclopedia that anyone can edit.” Instead of showing up immediately, as was past practice, any comment on a Wikipedia article about a living person now remains invisible until it is approved by a trusted and experienced editor.

Wikipedia’s new screening is not the only reputational hurdle of this kind. Over the summer, Gawker Media (the online company running the Gawker, Lifehacker, Gizmodo and Jezebel blogs, among others) introduced a new system of moderating comments. Only those comments made by starred users would be visible by default. Users earn stars when other, highly-ranked users choose to promote their comments.

Having users police other users allows Web sites like Wikipedia, Gawker and eBay to provide helpful ratings of reliability without instituting top-down certification. All of these systems provide a rating that is linked only to your handle on that Web site. Your behavior on eBay does not affect your ability to comment on Gawker. Yet.

As our day-to-day activities increasingly play out online, we are building up long records that may be used by others to analyze our fitness for hiring, dating or even participating in online activities. Meanwhile, programs like OpenID, GoogleProfile and Facebook are trying to make it easier to trace activities across Web sites back to one identity.

This is a potentially great development. The Internet and online activities have long been stigmatized as a labyrinth of unverifiable assertions, a place where anything can be faked. In a reputational economy, every source can be evaluated for reliability.

What is lacking is an open and understandable way to make these assessments. There’s no equivalent of a FICO credit score for our online identities, and there is no bevy of businesses offering to compute our online ratings and help us improve them.

Reputational economies are vulnerable to many of the same abuses as any other kind of economy. And if their workings are obscure, the few people who do understand how the system works can take advantage of others. This has already happened in online role-playing games like The Sims Online and Second Life, where players evaluate other players, generating rankings that can limit activity with the games. Canny players in these games make money by setting up racketeering schemes. They threaten to tag other users as untrustworthy, lowering their reputational worth, unless the victim pays a protection fee.

This kind of malfeasance isn’t limited to role-playing games. Extortion could be practiced in any reputational economy that relies heavily on peer ratings. Ignorance of a system puts you at risk of being hurt by cutting-edge scammers, or of harming yourself by accident. Not being able to monitor your reputational credit is as dangerous as not being able to untag embarrassing pictures on Facebook.

Data mining and reputational economies are powerful instruments, and, like all powerful tools, they can be dangerous.

My brother is going to be watching his credit score. I only wish I could see mine.

Leah Anthony Libresco is a junior in Jonathan Edwards College.