AER Energy Resources (AERN.OB) AERN has been an extremely hot penny stock, but the continued high volume of promo emails is alarming to some. Shares are up over 20 percent at the time of this entry, but the Reg Sho, Rule 201 is now in effect. Rule 201 is often a sign of naked short selling. Keep your eye on this one for no other reason than to watch the outcome of bears versus bulls.