Bitcoins are fairly similar to stocks in a way so I am not quite sure if there is a maximum price at which people would stop buying them. As the price of bitcoins continues to skyrocket (I believe its value reaches 1900 USD today), investors will be more likely to buy in as they would like to see the value of their assets increase. What would stop people from buying bitcoins however is if people were to start selling their bitcoins at a faster rate than it is being purchased, leading to a downward spiral in which more and more people continue to sell while the value continues to drop. That is essentially what took place during the Great Depression quite a few years ago. Let's hope that doesn't happen anytime soon! Though despite the cyclical nature of a stock crash, bitcoin has proved itself unwavering and has survived many 'deaths' over the years. Perhaps the root cause would be the stalwart believers in the decentralized currency, supposing that a lower price would simply be a positive opportunity. Basically if they price would start to plummet, bitcoin holders would start to sell off all their bitcoins. Then, when the price has reached its low, they buy back their bitcoins for a much lower price.