The video from @Ivanontech is very good. It provides an alternative view of the subject. He is breaking it down nicely as to what can take place and why and how this all works. In response to his video, I have made the following comments: Great video, Ivan, as always. Missed this one last month, was busy with work. I call "accidental" collisions all of the three instances you have described. I agree that trying to guess a private key is a special thing that might be done by quantum computers at some point in the future, may be. There are quantum resistant solutions to which bitcoin will have to switch as well. I place the word accidental in quotation marks because mostly what I'm referring to is generating and storing keys to various addresses on purpose. Let's say for a bad actor it is not too much to run an AI bot say on a dozen of machines doing just that and matching addresses against the bitcoin database of existing addresses. Day and night, and we don't have to be "sitting here" for a millennium. We can go to sleep. As adoption rises, there are more addresses generated every day. I am sure that there are other ways to do it as well, especially as our computational capacity goes up. The humans have a proven record and if a universe is within a reach, rather than going too far to check out the milky way, might as well explore it in numbers :) All we need is to increase the odds and eventually a collision will occur (even if after ten years). Now imagine what this will do to the entire crypto space. The solution will be developed by some new currency that will be accidental collision and quantum resistant. I entirely agree with you on the title of the video: Bitcoin will never run out of addresses so that each person on the planet for the next hundred years has a million of them, new address for every purchase or transfer in each individual's lifetime and we will still have more than enough addresses to keep going. This does not mean though that a "helped" collision may not occur sooner than we are envisioning.