Sorry for rezzing this thread but I have some followup questions:
Assuming the barbarian example in the initial post, If an ally is in the path of the charge can he become an overrun target and then simply allow the barbarian to pass unchallenged allowing you to charge through an ally? If so does the ally and any enemies allowing the barbarian to pass unchallenged: 1 add to the cumulative -2 penalty and 2 take damage from overbearing advance?
Lastly, assume the barbarian is under the effect of an enlarge person spell and is now large, if one of the overrun targets is still sharing a space with him at the conclusion of the charge is it a legal charge?
I'm asking because all of the above is likely to become a situation in my game soon.