Less than a week after Twitter unveiled Vine, the video-sharing app apparently has developed a porn problem.

Released Thursday, the app for iPhone and iPod Touch lets anyone create and share six-second clips, but it also has become a popular venue for male genitalia and pornographic movies taped off TVs and laptops. As first pointed out last night by The New York Times' Nick Bilton, searches for #porn, #sex, and other associated tags brings up a handful of videos featuring male exhibitionism and other activity.

While Vine's terms of service don't expressly forbid sexually explicit content, Twitter does encourage users to use good judgment when posting content:

You are responsible for your use of the Services, for any Content you post to the Services, and for any consequences thereof. The Content you submit, post, or display will be able to be viewed by other users of the Services and through third party services and websites. You should only provide Content that you are comfortable sharing with others under these Terms.

However, Vine users can flag videos they find offensive. If clips receive enough complaints, Twitter will add a warning still to the beginning of the video that users have to bypass to see the clip, a Twitter representative told CNET.

"Uploaded videos that are reported and determined to violate our guidelines will be removed from the site, and the user that posted the video may be terminated," the representative said in a statement.

Long an advocate for freedom of expression, Twitter has been reluctant to censor tweets. A year ago, the microblogging site announced it would be willing to remove tweets on a country-by-country basis when there are local restrictions against specific content in the tweets.

While the NSFW content might not violate Twitter's TOS, Apple's App Store guidelines state that "apps containing pornographic material, defined by Webster's Dictionary as 'explicit descriptions or displays of sexual organs or activities intended to stimulate erotic rather than aesthetic or emotional feelings,' will be rejected."

Apple recently removed an app called 500px, presumably because of its photo-sharing capabilities, which might allow users to search for and find naked bodies. CNET has contacted Apple for comment and will update this report when we learn more.

Updated at 3:45 p.m. PT with Twitter comment.