Why did Bitcoin lose value so fast in early January 2015? What on earth is driving the price of Bitcoin and other alternative currencies down lately? It's one thing for it to go down a bit but losing practically 80% of its value in less than a year? I feel like bitcoin is coming to a complete collapse. A list of the most important factors and a detailed explanation would be great guys.
Adding to my answer on What are some of the proposed ideas to why the Bitcoin dropped to sub $400 in the end of summer 2014?, which I think is still mostly accurate:

Bitstamp loot

There are about 19k bitcoins held by the hacker that raided Bitstamp. While, as far as I know, they haven't found their way back into the market, it is an amount that would impact the markets if it were dumped. It is possible that some speculators were expecting a dump, and tried to position themselves to buy low. Such a dump in itself could have scared the already skittish market into further dumps.

Bitstamp has no trading fee until 19th

While Bitstamp seems to have weathered the hack well-enough, they are not taking any trading fee until the 19th. The fee usually being 0.2% – 0.5%, trades on much smaller movements are currently profitable. As Bitstamp is still the most important Western Exchange, this might have spiked a new dynamic.

The loss in value

Markets amplify the current trend. The loss in value is causing fear, leading to further dumps, creating a catch-22.

Russia banning Bitcoin websites

Bitcoin supposedly was a hip way to withdraw money out of Russia for a while. Although Russia had been rattling with their saber a while towards Bitcoin, they are finally starting to take action by blocking Bitcoin services there now. This might induce a trend of Russians moving out of Bitcoin.

Butterfly Labs has to sell their stash to confirm with financial obligations

Apparently, Butterfly labs has been ordered by court to refund their customers. According to rumors on reddit, they have been selling thousands of Bitcoins and are still sitting on more than 90k.

Mining operations sliding into unprofitable ranges

A bunch of mining operations, as for example CEX.IO, have cited that the current price makes their mining unprofitable. To cover financial obligations, they have to liquidate a larger percentage of their bitcoins than before, perhaps even their saved holding they were hoping to carry over to the next bubble. With the dropping price covering their obligations by liquidating bitcoins only gets more bitcoin-expensive.

Bringing oneself in position to buy takes a few days

When the price quickly lost value, few of those that were interested in catching up the cheap coins were already in position to buy. As it takes a few days for money to be transferred to exchanges, the buy reaction is a bit delayed in comparison to a price drop.

Especially on Bitstamp where deposits were closed for a few days during the slump in the aftermath of the hack, people were probably waiting for the dust to settle. In fact, a lot of the deposits from Bitstamp were immediately withdrawn on reopening. 

Once the dust settled, and people started to realize that Bitstamp actually appeared to be in good shape, it still took a few days for potential buyers to transfer money to Bitstamp, which would explain why the price was somewhat shifted lower on Bitstamp in comparison to other exchanges for a while.

As usual: I'm a computer scientist, not knowledgeable in economy beyond what I read here and there. Please do not consider this investment advice; I have been wrong before. Please trade responsibly.