I have heard this mentioned before. I think it was quite unlikely that Jackson's death was intentional. Considering the circumstances surrounding the event (heavily wooded area...frontline of a major army during a major battle...poor lighting and visibility) it was probably an accident.

Conspiracy theories do tend to pop up after great tragedies or events. While "fragging" (as it later became known) or the killing of unpopular officers during battles has occurred in American history, I believe most friendly fire deaths are accidents.

Although, if someone ever found compelling evidence to suggest foul play, it would be interesting.