Normally, updating content means replacing a file - for instance, if I update a blog post, then people will see the new edited file, and not the old one. However, with IPFS, both versions of the file will be accessible in the network. It's not a matter of replacing: you add the new one, too. This raises the question: how do we actually update our links, so that people will see the new version of a file? They can't go to the file's location, because IPFS locates files by looking for their hashes (that's what content-addressed means). So, you need to have a way of pointing people to the new hash easily.