Just a warning: blurring pixels in sensitive photos like this is often insufficient. Always black out the information instead (and make sure to flatten the image! and not save it as e.g. a pdf with a black bar over it which has actually happened before too)
That attack is more useful against a mosaic than a straight blur. In this case, to attack successfully, the attacker would have to lay out every possible passport with the letters in the exact position as they'd be printed, because there is a pretty strong blur applied. You have an F and the line of < characters to work with, you know about how long her given and surnames are, and you have a frame of reference for the rest based on how much of the bottom line the author had to blur. Not much else. You also don't have a guarantee that the blur is straight out of Photoshop and contains what you are trying to reverse; looking at it, I don't think it is the actual passport data. I think it was modified then blurred.
I'm happy to be proven wrong, but I think this one is impractical.
The link you provided doesn't provide us with any insight into what the NSA's state-of-the-art might have been.
This NIST publication says: "for ATA disk drives manufactured after 2001 (over 15 GB) clearing by overwriting the media once is adequate to protect the media from both keyboard and laboratory attack."
Tech changes have "altered previously held best practices regarding magnetic disk type storage media". It does not seem to confirm that multiple erases were unnecessary before.
It's quite possible. Not only is it possible to perform deconvolution, but since you know that you're looking for text data, and you even have the font, you can do much better. You can iterate through millions of names very quickly and find which one, once blurred produces the best match.
They actually have an example for a regular blurred jpeg at the end. And yes, a camera shake may big difference to a regular blur, but then again, an actual regular blur (so an unfocused lens instead of a moving lens) is less often the problem.
Wow, I had meant to have another sentence saying that it is probably still possible based on the "blur" technique used. But... yeah, I clearly did not say that.
I would assume most of the time people "smudge" the data they want to be removed from a photo. Though, as stated, adding new information to the image has got to be the best way to do this. (a blackout.)
1) Obviously you're talking about traditional spinning platter drives, and not SSDs.
2) The complete drive needs to be overwritten to be sure all data has gone. The safest way to do that is to use an ATA secure erase command. This will overwrite all the sectors marked as bad. DBAN is good, but it will not overwrite sectors marked as bad. (The risk from this is small.)