what would it take for the Bitcoin price to drop less than a dollar? I don't understand why the prices have actually dropped these days so much. Some forums say that people are selling, so what? People are selling, and people are buying, the bitcoins don't disappear they just change hands. Then why does the price drop?

And assuming this is the case, then theoretically speaking, what would it take for the price to drop lower than one dollar?
This is all speculation in a very new technology. I'm not an expert in economics, but there are irrefutable facts that's some of the "cultists" will not entertain. There are, simply put, 2 types of Bitcoin advocates:


Those who see in binary; black and white, moon and doom - more often than not Bitcoin's "success" is solely judged in fiat conversion
Those who are more pragmatic; the people who understand that MySpace gave way to Facebook


The most dangerous attitude is the former, because there is no acknowledgement that Bitcoin, in its infancy, still has a long way to go. The Blockchain is the key technological advance here. It is already being adopted by companies like Blocktech Group for commodoties and smart contracts. That may involve building on top of the Bitcoin blockchain, or it may mean an entirely new Blockchain purpose built for a corporate interest. 


  As a thought experiment, imagine there was a base metal as scarce as gold but with the following properties:
  
  
  boring grey in colour
  not a good conductor of electricity
  not particularly strong, but not ductile or easily malleable either
  not useful for any practical or ornamental purpose
  
  
  And one special, magical property:
  
  
  can be transported over a communications channel
  
  
  If you redact "over a communications channel" you end up with depleted
  uranium...


-Satoshi Nakamoto

So with that in mind, realise that there is no certainty of a $10,000 BTC price in the future. Perhaps $400 is what BTC is worth? Perhaps $1100 was well and truly over its true? These questions can only be answered with time and with development. There's a very small team looking after the code while speculators search for answers about why they're not rich yet. Perhaps we need to add value to Bitcoin instead of expecting, like it's everyone's destiny, that BTC will go to the moon in price. Will it drop to $1; only if the Bitcoin P2P network dies. I think the best think anyone can take away from this is it is possible to separate a Blockchain from Bitcoin. A long term outlook would serve everyone better than daily stresses over price volatility.