A volatile stock market and tightening credit market made for another rough week for investors. Is there another shoe to drop? In this installment of "Fool Video," Motley Fool senior analyst Tim Hanson explains why sovereign wealth funds may spell trouble for your portfolio. Stocks mentioned in this video include PetroChina (NYSE:PTR), CNOOC (NYSE:CEO), New Oriental Education (NYSE:EDU), and Petrobras (NYSE:PBR).

More Fool fare: