why did bitcoin suddenly spike? about 2 months ago the price was at about 140 USD per coin, but a couple days ago I checked and it was well over 1000! 
what caused the sudden spike in value and will it continue to grow?
TL;DR: No idea, and your question's unanswerable in the first place :)

Why does a national currency rise or sinks in value? Why do a company's shares do the same? You will never get definite answers for these or your original question unless you manage to get into all the participants' heads to know what they were thinking of. Meanwhile, you can listen to pundits or draw your own seemingly informed conclusions.

A couple months ago, when there were these rumors about the US government possibly becoming unable to pay its debtors, Bitcoin started going up and up to the point of doubling its former value - obviously a lot of people were viewing it as a possible haven should the dollar fall. After it was clear such fears were based on nothing the Bitcoin fell down from that high.

But then it started climbing again, reaching again its former high mark, then doubling it, then doubling again... Looking at the graphs of this spectacular pike its clear to me a good part of that was a bubble caused by speculators jumping to ride the wave, but exactly which event triggered the upwards trend in the first place... to this day I honestly don't know.

Some say it's the hearing at the US Congress giving it legitimacy. Some say it's closing the Silk Road cleansed its image, though others say this event caused it's value to fall a bit. Some say it's even more interest by the Chinese... no single event can be clearly linked to this surge in value as was the case in the past with, e.g., the events in Cyprus.