Dr. Robert Shiller's checklist on how to predict if something is a bubble or not.
* Sharp increases in the price of an asset like real estate or dot-com shares
* Great public excitement about said increases
* An accompanying media frenzy
* Stories of people earning a lot of money, causing envy among people who aren’t
* Growing interest in the asset class among the general public
* “New era” theories to justify unprecedented price increases
* A decline in lending standards
Now most of these points can be applied to bitcoins, almost 200% growth in the last few months. Dot-com was a bubble and it popped, and bitcoins are similar to it in terms of technological advancement, almost all technological breakthroughs in the past have caused a substantial impact on the market, no matter how small it was, but the whole concept of bitcoin is different. So is it a bubble? Yes and no. Obviously anyone would get a bit skeptical when a currency has such a tremendous growth in a very short period of time. But mass adoption can be logically applied as a reason behind it.
Being a currency, as far as the user base increases + the areas where bitcoins can be applied increases, it would be in demand, and would not just go out with a burst.