The banks don't like bitcoin.
And so the day tripper investors pull out and perhaps invest in shares say via the Lloyds bank share trading platform or whatever. At the end of the day any money that is not in a regular bank is not helpful to the banks so the banks are retaliating.
This was an inevitable part of the bitcoin experiment and it is fair bet that Bitcoin will survive it but the hit to its value is obviously anyone's guess right now. Probably more importantly is what the banks will do next with regards to fight any possible recovery or growth - are they any more capable of fighting it than media creation companies are of fighting the pirate bay?