Yesterday Steam released a patch but never told anyone about what was going to happen. The result is people logged in to Steam and found half their games required 400-600 MB patches.
In reality Steam discovered, decades after the invention of the directory tree, that they could create a single sub-directory tree to store all of the the standard redistributable files most games need. Things like MS C, MS C++, DirectX 9, 10, 11 etc.
Fortunately you only need to download a single 'game' patch instead of one for every single game. In the long run this is actually a good thing since you will have recovered all of that storage space taken up by having multiple copies of the same thing on your drive.
Of course Steam doesn't tell you that. They'd rather you get pissed about all the updates and then breathe a sigh of relief when you discover most of them are ghosts.
"I used to think the worst thing in life was to be all alone. It's not. The worst thing in life is to end up with people who make you feel all alone." Robin Williams