In an age where your boss, coworkers, parents, and even (*gasp*) grandparents are finally joining social networks, we are all more aware than ever that we had better keep things relatively clean. And if you were someone who joined MySpace, Facebook, Flickr, or a number of other sites years ago, you may have more cleaning up to do than usual—after all, back then, you were probably young(er) and dumb(er), posting silly pics of your drunken escapades or questionable updates regarding your unusual interest in English cucumbers.

If you delete questionable images of yourself, you may be in the clear—or you may not, depending on the social network. As it turns out, some social networks delete your images right away while others hold onto them even after claiming they've been deleted. This was the discovery made by researchers at Cambridge University last month when they found that images deleted from social media sites are often left on the server, ripe for anyone to embed elsewhere or link up.

We put this finding to the test and found that some of the most popular sites on the Internet do, in fact, keep images on their servers after you delete them. On May 21, 2009, we deleted photos from four of the networks most used by the Ars staff and readership and monitored them for six weeks. The four networks we checked were Flickr, Twitter, MySpace, and Facebook.

First, the good news. Both Twitter and Flickr deleted our photos within seconds. Direct links to the photos in question broke after a quick hard refresh, so you can be sure that your salacious pictures mistakenly posted to Flickr while inebriated will no longer be accessible to your enemies (assuming they didn't copy them to their hard drives, that is).

Facebook and MySpace, however, did not fare so well. As of this writing, both images we used are still available on Facebook and MySpace servers despite having been "deleted" in May. (For embarrassment's sake, here are my two photos that were deleted from Facebook and MySpace; depending on when you read this article, these photos may or may not still be up).

Both sites claim to delete user info immediately, so we reached out to the companies to see what they had to say about the findings.

"MySpace takes the safety, security and privacy of its users very seriously and immediately deletes user content and profiles in their entirety when requested to," MySpace spokesperson Amy Walgenbach told Ars via e-mail. "We are aware it can take longer for images to be removed from third party servers (servers from the vendor we work with) and are actively working to address this."

Facebook offered a similar statement, but went a step further by claiming that third parties could not access the information even though it is retained on the server. "As stated in the Statement of Rights and Responsibilities, the governing document for the site, ‘when you delete IP content, it is deleted in a manner similar to emptying the recycle bin on a computer. However, you understand that removed content may persist in backup copies for a reasonable period of time (but will not be available to others),'" Facebook spokesperson Elizabeth Linder said. "We are working with our content delivery network (CDN) partner to significantly reduce the amount of time that backup copies persist."

This looks obviously false—said "backup copies" are indeed accessible to anyone on the Web. We tried to get clarification from Facebook on this point but received no response. Either way, the lesson is clear—if you don't want to give your enemies blackmail material, don't upload questionable photos in the first place. If you already have, just hope that no one has a direct link... or be prepared to blame all your transgressions on an evil twin.