Are some companies easier to predict than others?

To better test out Encog 2.0 on large training sets I am beginning to conduct research for predicting trends in the S&P 500 index. I am starting out simple just using historic price information to predict future trends. I will post this research, as it progresses, to the following URL:

http://www.heatonresearch.com/market/

There will also be forum posts as this progresses. The first experiment, which was just completed attempted to determine if some companies on the S&P were more predictable than others. You can see a chart of this training here:

http://www.heatonresearch.com/node/1020

The forum post has more information here:

http://www.heatonresearch.com/node/1021