O Romeo, Romeo, wherefore art thou Romeo. Even if you failed English class, you'd recognize that phrase anywhere. It's from Shakespeare's Romeo & Juliet. But would you recognize this phrase: O Romep+ Rpldo wiepffnre arr!riov Romep@. That's Shakespeare too. If Shakespeare was compressed over and over again by JPEG.
Tom Scott created a little experiment to poke fun of the lossy nature of JPEG. Every time you edit and save a picture in JPEG, you're going to lose something from the original. Even if you don't see it (and most of us don't see it), it's gone forever. Scott thought it would be fun to see what we would lose in JPEG if we saw converted it in text and boy it garbled up Shakespeare real good.
Scott basically loaded Shakespeare text as RAW in Photoshop and outputted the text to JPEG at different quality levels. As you can imagine, Photoshop's minimum level destroys Shakespeare while the maximum level still changed things up. Scott says:
Even on ‘maximum’ quality, almost all the characters are replaced by their neighbors in the alphabet. On an image, that would be a minuscule change in color, undetectable to the eye: but rearranged into a different form, even ‘maximum’ quality is enough to render the text a significant challenge to decipher.
This doesn't exactly mean never ever use JPEG ever again (since images are much different than text) but it goes to show how things can degrade over time, even digitally. You can see more of Scott's fantastically fun work here. [Tom Scott via Laughing Squid]