(A screenshot from Wikipedia.org)

Paid editors have long been Wikipedia’s dirty secret. Sure, the Internet’s fifth-largest Web site may trumpet itself as a crowdsourced compendium of human knowledge … but there’s plenty of evidence that at least a little bit of marketing, reputation-scrubbing and good old-fashioned lobbying go down behind the scenes, too.

There was that episode when a bunch of Hill staffers removed unflattering, factually accurate information from their senators’ Wikipedia bios. Or the discovery last year of a vast “sock puppet” network, where fake users talked up small Silicon Valley start-ups for pay.

Now, after internal investigations (and a slew of articles with headlines like “Is Wikipedia getting worse?”), the world’s largest encyclopedia is officially acting against the problem: As of Monday, all editors must explicitly disclose if they’re being paid for their work.

“We have serious concerns about the way that such editing affects the neutrality and reliability of Wikipedia,” the site’s parent foundation, Wikimedia, said in a statement. “The change to the Terms of Use will … empower the community to address the issue of paid editing in an informed way.”

Here’s how the changes to the Terms of Use work. Historically, Wikipedia has been edited by a frequently anonymous, predominantly male corps of volunteers — roughly 31,000 people were active on the English site in 2013, per the MIT Technology Review. For most of those people — good-faith volunteers, academics, etc. — editing under the new terms will not change. But anyone editing quid pro quo must disclose that in their user profile and on the back-ends of the pages they edit. (Previously the site had barred deceptive editing — but not defined what disclosure paid editors had to make.)

So for instance, if I noticed that the Washington Post page was out of date and I updated it voluntarily, on my own time, I wouldn’t have to disclose that I’m an employee. But if my editor slipped me $20 or a free day off to do it (which, hey editors, I’m available!), then I’d need to add a line to my Wikipedia bio and the “talk page,” or editors’ discussion board, for that wiki: “I work for The Washington Post and have been hired to update its Wikipedia article,” or something to that effect.

Wikipedia’s overseers believe this is a big win for transparency and accuracy on the site; it does, in theory, let other, more neutral editors keep an eye on the potentially biased antics of their paid peers. But there’s no incentive for disclosure, besides the wishy-washy “greater good.” And unfortunately, Wikipedia’s greatest asset — the anonymous volunteer masses, eager to pitch in on everything from toilet paper etiquette to intra-site wrangling — are also, in this case, its curse. There’s simply no way to conclusively detect when an anonymous person is editing for pay. Which means there’s no way to conclusively enforce it, either.

“We expect most people will comply with the change,” said Wikimedia’s Eric Harris. In terms of enforcement, he added, “we expect that the community will be effective in assessing and dealing with the situation.”

Will they be effective? Probably, to an extent: It was Wikipedia editors, after all, who first discovered the sock puppet ring to begin with, and it’s Wikipedia editors who police against other mistakes and breaches of policy.

That said, Wikipedia will never completely rid itself of secret PR or lobbying interests, just as it’ll never rid itself of occasional bias or misinformation. Those things are simply inherent risks of self-organization — and Wikipedia is, at this point, one of the largest experiments in self-organization the Internet has left.