Maybe something completely preposterous, there are always people who will believe even the most absurd and unbelievable claims. For example:

* Scientists discover that the "security" of SHA is entirely based on an unproven math conjecture.

* Operator of a major Bitcoin exchange  flees after stealing all his clients' bitcoins.

* Founding member of the Bitcoin Foundation is arrested, charged with using Bitcoin exchange for drug trafficking.

* Bitcoins are being stolen from accounts of major exchange https://bitcointalk.org/index.php?topic=324918.msg4840947#msg4840947

* FBI documents reveal that it has the means to trace bitcoin transactions and seize bitcoins without the owner's knowledge.

* Alternative cryptocoins appear, threaten to reduce demand for Bitcoin in the future.

* There are millions of hoarded Bitcoins that were bought for less than 10 US$ and may be dumped at any moment.

* Economist warns that Bitcoin's price will fall to less than 10 US$ as soon as the market realizes that it will fall to less than 10 US$.

* Media loses confidence in established Bitcoin leaders, turns to the Wall Observer thread for reliable market analysis.