I will go with #3, stupidity, LOL! But it could be someone selling 5000 shares at the low bid to trip stop loss orders to fill their own bid orders for more shares. That is why it is so dangerous to use stop loss orders on penny stocks. The MM's are the only ones that see stop loss orders, and they love to take then out by shorting the stock and grabbing the cheap shares tripped by the sell, so they can turn around and sell them at the ask. I have rarely been able to buy at the bid on this one.
A few months ago some one bought 100,000 shares at .18, and the MM's immediately walked the ask and bid down for the next 3-4 days down to .10/.12 until they scared enough people into selling them enough cheap shares to cover, as the 100,000 share sale at .18 must have been sold short by MM's, and the MM's panicked! This is not a good stock to daytrade, unless you have lots of cash, and know how to manipulate the price like an MM does. But It is one to buy and hold for now when the cheap shares are offered IMHO. If you bought at .16 to .18, do not panic, that is what the MM shark feeds on!
I have been in this stock for 2 years, and my average cost is .18 right now. I am holding out for at least 50 cents to $1 on the next rally, no mater how long it takes.