That can be ruled out. Bit rot does not appear suddenly in a widespread manner and does not cause very similar visual effects in a variety of images. Also the original images are still available, just new modified versions were shown. To me it looks like a new compression algo gone wrong.
A bad bit wouldn’t even be noticeable in an image. Changing one bit would make literally no difference. Artifacts look like something the compression algorithm has messed up. Also since the images are actually intact according to Google this is likely just the compression algorithm used to browse the images.
Update: my limited knowledge on this is proof I’m wrong.
A bad bit might have no visible effect at all (e.g. Affecting part of EXIF metadata, or a totally black pixel turning again very close to total black) or can corrupt the whole image (flipping a bit in the file header or cosine quantization table).
As a total layman when it comes to storage: Don't they use forward correcting codes to make sure a single bad bit can reliably be detected and flipped without affecting the data at all? Or are these used only for data transmission?
I've encountered older digital photos where a small corruption affects all of the remaining parts of the image as it is presumably recorded in some linear fashion as shown in this Wikipedia entry's "Visual example."
