Try this: Take a photo and upload it to Facebook, then after a day or so, note what the URL to the picture is (the actual photo, not the page on which the photo resides), and then delete it. Come back a month later and see if the link works. Chances are: It will.

Facebook isn’t alone here. Researchers at Cambridge University (so you know this is legit, people!) have found that nearly half of the social networking sites don’t immediately delete pictures when a user requests they be removed. In general, photo-centric websites like Flickr were found to be better at quickly removing deleted photos upon request.

Why do “deleted” photos stay there so long?

The problem relates to the way data is stored on large websites: While your personal computer only keeps one copy of a file, large-scale services like Facebook rely on what are called content delivery networks to manage data and distribution.

Here is a sneak peek on how Facebook stores millions of photos on their server:

[They use something called Haystack file storage system, which basically means Haystack stores photo data inside 10 GB bucket with 1 MB of metadata for every GB stored. Metadata is guaranteed to be memory-resident, leading to only one disk seek for each photo. Haystack servers are built from commodity servers and disks assembled by Facebook to reduce costs associated with proprietary systems. Cache remains a first line-of-defense to Haystack lookups, quickly processing requests and loading images from memory cached where appropriate. Haystack provides a fast and reliable file backing for these specialized requests.]

P.S: if you don’t understand what I’m talking about, its ok ….

Google and Microsoft also use almost the same technology to store the whole WebPage as cached pages.

What is Google webpage Cache?

Google takes a snapshot of each page it examines and caches (stores) that version as a back-up. The cached version is what Google uses to judge if a page is a good match for your query. Click here, for more information about Google Cache.

Moral of the story: Those drunken party photos you don’t want people to see? Simply don’t upload them to the web, ever, because trying to delete them is a tough proposition.  :) makes you want to think twice huh?…. Stay secure & have fun !!