Every investor needs to consider both the bull case and the bear case when it comes to a stock they own. In this video, Motley Fool analysts Charly Travers and Austin Smith discuss some of the reasons to be bearish on Finnish phone maker Nokia (NOK -0.54%).

As Charly points out, investors need to be rational and look at the Lumia sales volume, the big concern. When the company reports its quarterly numbers in January, unless the Lumia numbers are high, investors should take a bearish stand.

Nokia needs to gain some serious market share in North America, as presently Nokia virtually has none right now. The company needs to sell millions of units and if it can't do that, then investors should be rational and walk away.

Finally, being married to your investment in Nokia isn't a good idea unless the numbers start materializing. Investors need to be pragmatic and analyze the risk-return setup here.