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They say almost anything goes on the Internet. Except, that is, when the lawyers become involved.

That’s especially true of late for Reddit and 4chan, two of the web’s wildest, no-holds-barred community-driven sites. Both places are rooted in old-school web culture, and consist mostly of anonymous users posting links and photos to message boards as topics of discussion. Both regularly have tens of millions of visitors come to view anything from cute animal pictures to grisly, actual videos of people’s deaths to, most recently, the naked, private cellphone photos of the actress Jennifer Lawrence.

Last week, Reddit was one of the major hubs for finding and distributing a cache of nude celebrity photos, sending the web and media worlds into a tizzy.

But the sites, which have long been known for their freewheeling approach to content hosting and user self-governance have started to change their tunes. Over the weekend, Reddit shut down all forums on its site in which users were posting and linking to the nude celebrity photos, a rare action for a company that has mostly taken a hands-off approach to user postings.

Similarly, last week 4chan imposed a D.M.C.A. take-down request policy for the first time in the site’s 11-year history.

Reddit said its moderators were unable to keep up with a torrent of requests under the Digital Millennium Copyright Act to remove the images, made by those who own rights to the photos. After a moderator removed a post in response to a D.M.C.A. request, another post would pop up in its place. Taking down the entire forums, Reddit said, was the only way to avoid playing a never-ending game of “whack-a-mole.”

The moves came amid an continuing debate over the role websites play in hosting objectionable content online, and how much user-generated content platforms should or should not interfere with what their users post. Twitter, for instance, has faced increasing pressure to protect users from abuse and hate speech on its service, while YouTube has been used at times for distribution of horrifying videos.

Despite its content removal, Reddit continues to maintain its hard-line stance on issues of free speech, even as it decided to take down the forums in question. The company said it had always dealt with D.M.C.A. removal requests by redirecting rights holders to the companies that host the photos on their servers. It has also held a zero-tolerance policy toward some content, such as child pornography.

“We uphold the ideal of free speech on Reddit as much as possible not because we are legally bound to,” said Yishan Wong, Reddit’s chief executive, but because the company believes that the user “has the right to choose between right and wrong, good and evil,” and that it is the user’s responsibility to do so. His company blog post was titled “Every Man Is Responsible for His Own Soul.”

Yet Reddit finds itself in a particular bind. The site has lately redoubled its efforts to become a thriving, profitable business, stepping up its advertising efforts and going on a hiring spree.

“The Achilles’ heel for a lot of these sites is that their plans to monetize themselves often directly affect how they structure their platforms,” said Jeffrey Chester, the executive director of the Center for Digital Democracy, a privacy advocacy group.

Reddit is also reportedly in the process of raising more than $50 million in venture capital, according to the technology site Re/code, which could value the company at upward of half a billion dollars.

Reddit, then, may have to rethink its classic laissez-faire approach to content, especially if it wants to be courted by big-budget advertisers.

“They’re trying to have it both ways,” said Marc Rotenberg, executive director at the Electronic Privacy Information Center, a Washington advocacy group. “If you’re highlighting information and generating revenue off the advertising associating with your readers’ interests, it’s hard to say, ‘Gee, how did those photos get there?’ ”

Still, if Reddit decides to change its approach in the future, it must walk a fine line between appearing attractive to marketers while not alienating the very community of people it has attracted in its nine years of existence.

In the meantime, Reddit will continue to trumpet its philosophy of letting its constituents use their own moral compasses to guide what they will or will not post — even as it has decided to take down some of that content.

“Virtuous behavior is only virtuous if it is not arrived at by compulsion,” Mr. Wong said. “This is a central idea of the community we are trying to create.”