Well Cat Schwartz, of Tech TV, recently learned a valuable lesson about computers—forunately she learned the hard way. Recently she posted some unreavling pictures of herself on her blog site—or at least what she thought was unrevealing.
However, there's an important issue to keep in mind about software—many applications save "meta data"—data that is "hidden" from the user, but embedded in the file. For Microsoft's Office products typically will keep track of all your changes to the document. This means even after selecting and deleting text from your document and saving the file, the data you delete may still be recoverable. That's why it's important to never, ever put any content into a document that you don't want viewed. You should be able to remove that hidden data in an Office application by simply opening a new document and copying all the data to a new file.
Anyway, back to Cat's situation. The pictures she was posted were editing in Adobe Photoshop. By default, Photoshop will save a thumbnail preview of your JPEG images as meta data within the file. It does this because it speeds up displaying thumbnails in their thumbnail view. The problem with this, is that the meta data isn't always updated. If you don't use the "Save As" option to save the file in a different file or don't make "dramatic" changes to the file, then the thumbnail won't be updated. You're still probably wondering where I'm going with this.
Cat's been handling the situation pretty well, and I think her new picture/last blog entry is appropriate. So just remember, if you put something in a document and then "delete" it, don't expect that the information is "truly" gone. If it's very sensitive information, you're best bet is to cut-n-paste it to a new document.