In your explanation of shorting one issue is finding a broker that has shares you can borrow and finding penny stocks is next to impossible - especially non-SEC reporting OTCM companies.
Then there is the $2.50 rule. Meaning that for stocks below $2.50 (with Scottrade it is $5) you have to have $2.50 for each share borrowed in a margin account.
If you could find and borrow a million shares of GRCU stock - you would need $2.5 million in a margin account.
At the current price you would control $50,000 in GRCU stock but have $2.5 million in a margin account.
If the price dropped to .0001 - the profit would be $49,900 but your $2.5 million would be unavailable during the time it takes to drop to . 0001. Then there are assorted broker fees.
It just isn't economically feasible to short penny stocks.
There will be someone that posts SureTrader will allow you to short pennies without a margin account - but that isn't any longer true.
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