Let's say there are groups of shorts which I believe to be the case here. 16 million is not all hedge funds and sole individuals. So let's assume for the sake of argument this is the case. To hold the stock you need to buy shares. So you must own shares(assuming you don't want to buy back your short position). When the stock rises a little you simply sell your shares on a small move to push it down multiply this by the power of many and you will see bigger moves down. Once it gets to a lower level simply repeat the process. No extra shorting required. How many times does this have to happen to discourage any significant buying? I see about 1 million shares shorted each month from January. This does not sound like a lot but if you time your sells late day and at critical times you get the max out of the shares you buy to always make the stock look weak and discourage people from buying.
Remember when we saw the stock drift down to $2.70 recently on lower and lower volume, this is evidence of discouragement. You follow the boards so you know the mood. If people are discouraged they either sell or stay away they certainly don't buy more, at least most people won't. The declining volume was evidence of that. Even now think about this lots of shares traded in the $3.20 to $3.40 area on the MSFT announcement, yet now people are reluctant to buy at $3.20. Look at how quickly the volume has fallen off and watch carefully how quickly shares are sold on the slightest rally.
I have no idea who these "short interest groups" are and why they would hold millions of shares this long into the game. Logic would have told me they made their money and should have began covering weeks if not months ago so I am always looking for people in the know on this subject Newbie. Short squeezes happen all the time, I just hope we get ours in Vringo.