In the video below, Fool analyst Matt Koppenheffer takes a look at three reasons investors might be bearish on AIG (AIG 1.70%).

Matt is a bull on AIG, but even bullish investors must take the time to consider the bear case for the stocks they own. 

The first concern for AIG is whether its core businesses, the property and casualty and life insurance businesses, are good businesses. It has spun off non-core businesses, making the core businesses very important. If they show signs of weakness, that could be a reason to sell.

Second is the CEO. Robert Benmosche has done a great job bringing AIG back from the brink, but he won't be around for long. Investors need to watch the transition. The hiring of a new leader who is not strong could be another potential reason to sell.

Finally, the brand damage done to AIG is significant. If customers remain biased, that could hurt sales.