Originally Posted by CountChocula
This used to be the case for some games, but it was fixed during 2011 with a client update that allows for smaller patches for large files

The way that Witcher 2 was designed, for example, required a huge 10-20GB file download for the first few patches as it would replace an existing large file. At some point in 2011, the Steam client was updated and this was no longer necessary

Yeah steam patched the process but my games sometimes still have to be redownloaded due to corruption during the patching. It's better now but rarely happens still.