The "REAL REASON" is a combination of the various things people have pointed out.
Gox Coins
The real reason is obvious! 800,000 coins stolen by MtGox are being slowly and carefully dumped on the open market, driving down the price.
The flooding of the market by the Goxxed coins will probably continue to keep the price low until they are all absorbed by investors and consumers .. how long will that take? No one knows.
Large Merchant Usage
Might be the effect of big merchants dumping coin as well...
Hostile Government Actions
Or hostile gov't regulation
Still coming off a huge bubble. Value of daily new coins exceeds value of daily new money entering the market
Or it's falling because 3600 coins a day are released and there's obv not $1 mil/usd flowing into the market on a daily basis to buy those coins. The price of BTC needs to fall ALOT more before it stops falling.
This is going to happen for another year and a half! then even once they halve it will be 1800 coins/day which is still alot for another 4 years! This pig ain't going anywhere for the next 5-10 years
Pump and Dump speculators, hedge funds, and any other trick that has been used to manipulate markets.
gox-illicit market-stamp coins are part of it. traders also have the trend and they are giving bitcoin the treatment. bitcoin was a largely untapped market for traders and they are schooling it. they want dumps, they want bumps, they want volatility. they want to see presumptins of support broken. my two pence says we r looking at 200 before this bear gets put back in its cage.
I would add diminishing confidence that bitcoin will evolve/innovate quick enough.