When you delete a photo that you had uploaded to a social network, what happens?

You might expect that it’s deleted. After all, why would Facebook, for instance, want to store that old photo of you and Aunt Hilda any longer than it has to? Even you don’t want that photo.

But according to researchers at Cambridge University, deleting your photos from popular websites isn’t a guarantee that they’ll actually be deleted.

The researchers uploaded photos to 16 popular websites, recorded the direct URLs to the images and then proceeded to delete them. 30 days later, their photos were still accessible on seven of the sites. One of those sites was Facebook, which tells users that their photos are removed “immediately” upon deletion.

A Facebook spokesman blamed the phenomenon on the fact that the photos were cached on Facebook’s CDN. Hardly an excuse after 30 days.

This simple but interesting study demonstrates that some of the most popular websites are pretty lazy when it comes to protecting the privacy of their users in the most basic of ways (eg. deleting their content when requested). This is why it’s so important to think twice about what content you do upload; once it’s up, you may not be able to pull it down.

Another interesting aspect to this: companies that don’t remove content after it has been ‘deleted‘ by the user are burdening themselves with additional costs. Even though one photo won’t break the bank, if you consider the possibility that some of these services are storing tons of content that isn’t being used, you could see how the costs could eventually be noticeable.

In my opinion, companies should remove content when users go through the motions to delete it and if you run a service that stores user-generated content, you should make sure that you’re doing so.

Photo credit: freeparking via Flickr.