No. 2: StemCells ( STEM) What's scarier than pitching an RNAi stock to an investor? Pitching an embryonic stem cell stock! Geron had the good sense to abandon its embryonic stem cell therapy program. StemCells perseveres for reasons unknown. The stock: StemCells began and ended 2011 the same way -- by raising money. In between, the stock lost 93% of its value.