The bitcoin craze of late raises an ethical challenge. Assume bitcoin will rise in value by many folds in the coming months and then drop to some sane level going forward. No one knows how the trajectory will take place. As an investor or gambler, do you buy it now in hopes of making a fortune before it falls and sell it for the gain? The ethical part is do you realize the gain at the expence of some other investors who are caught up in this craze? The equivalent comparison is these multi-level marketing schemes which is a reincarnation of the pyramid scheme. The people at the top of the pyramid will make lots of money at the expense of those at the bottom. What does one do?