It depends, the stock market can get overleveraged and overbought also.  It remains to be seen whether Bitcoins have hit that point.  The real question is who is buying Bitcoins now and why?  Many of the big early holders got their Bitcoins from mining, not through debt financed purchases.  Are new buyers buying with debt?  Are they buying more than they can afford, and will need to sell them soon?  Or are they mostly people who are intrigued by Bitcoins and just buying a few to take part in this cool system with some spare cash?  Once the suckers buy en masse, that's when it will probably crash, although whether it will be a mini-crash or a major crash will depend on who the majority of holders are.