Here's a possible explanation from Jim Sinclair:

http://jsmineset.com/

It has been the strategy of some hedge funds to pummel the prices of junior explorers in order to starve financially this very important segment of the minerals industry. I suggest to you that if you deduct the transactions that underwriters have made as intermediaries between junior explorers and hedge funds called PIPES, there have been practically speaking no underwriters interested in doing business with anyone but major gold producers.

The reason for this is simple. The hedge funds have so depressed prices that underwriters have no investment interest in them at all. For a junior to do a deal with underwriters or directly with a hedge fund on a PIPE basis is to offer their shareholders up as lambs for the slaughter. This covers the fund short but even worse motivates the fund with a guaranteed 15% to continue the short line.