Now that you mentioned bookmarks...
Every now and then I've noticed that a bookmark no longer works, i.e. the page it links to doesn't exist. That has proved true especially for big companies like banks, ISP's etc. who provide a lot of online services. They change the looks and functionality of their websites sometimes very drastically, like a bank who quit using Java on their online banking system. After a transition period the Java related page stopped working and people having that saved as a bookmark called for help. What if someone found a way to fake those obsolete pages. I don't know if that were even possible, after all the bookmarks direct to the right domain/server to their 404 page. Further, critical services most likely don't get on the "this domain is available" marketing pages. But who knows, there's people out there looking for flaws and backdoors, maybe one day an old bookmark can lead to a fake site. In a world of alternative facts we're more and more getting into the philosophical question of existence: Do we exist or are we just element's in someone else's dream?