The issue I have with Bitcoin is that people invest in it thinking that they are investing in cryptocurrencies, which is in your words what everybody knows will "be a thing". The problem is that they're investing in one very specific cryptocurrency, and there is no way of knowing if it's the one that will succeed. It's equally possible that we're seeing the pets.com or myspace of crypto-currencies -- failed projects in a genre that will change pretty much everything. It's the complete lack of understanding that worries me, and what makes me almost certain this is a bubble that will come down crashing hard.