As the Internet blossomed in the 1990s, many economists argued that the web improved information flow, reduced transaction costs, and thereby made capital markets more efficient. I believe this to be true. After all, the availability of information to all investors makes it even more likely that a new piece of data will quickly get factored into the price of a stock. According to the conventional wisdom, it's even harder to beat the market as an individual investor if stock prices so quickly incorporate new information. Emory Professor Paul Rubin expands upon this argument in a recent column in the Wall Street Journal. While he agrees that the web reduced transaction costs, he also argues that it may have inadvertently contributed to a greater propensity for bubbles. As he says, "It may be that bubbles and crashes are a natural part of capitalist markets. What's more, it may be that the very factors that have recently increased the efficiency of markets have also led to an increased propensity for bubbles."
In sum, because of the internet, people all around the world can quickly learn about "hot" new thing that seems like an attractive investmnet. Word can quickly spread to others through social networks, blogs, email, etc. Reduced transaction costs make it easy and cheap to then make a trade based on that new information. Soon, a bubble can emerge as word spreads quickly about a potential profit-making opportunity. Of course, it becomes a bubble when people are still investing long after the initial profitable opportunity was spotted; by the time the later investors have put money into the asset, the opportunity for a profitable return has greatly diminished. Yet, people are still chasing the idea. Why did the profitable opportunity vanish? Well, of course, the very efficiency of the market due to lower transaction costs has caused the "arbitrage" opportunity to vanish fairly quickly, yet many investors don't realize this until far too late. They are simply jumping on a social bandwagon.