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).

Petrobras is a Motley Fool Income Investor recommendation. CNOOC and New Oriental Education are Global Gains recommendations. Partner up with any of our newsletter services free for 30 days.

Neither Tim nor Mac owns any of the stocks discussed. The Motley Fool has a disclosure policy.