Depends. In the rule book there isn't anything for removing a pitcher for that. However, many leagues make their own rule for revoming a pitch for hitting too many batters'

I think its a coach's courtesy/common sense issue to remove a pitcher who is throwing wild--especially if she is clearly a danger to batters.

I agree with Mr. Bergren there...its' common sense not to put in a wild pitcher.
1) batters can get hurt when they shouldn't
2) pitcher will have alot of walks and possibly all the runs the other team has
will be majority because of WALKS!!!

an umpire can disqualify the pitcher after the fourth hit batter, if he/she feels its neccesarry.

As Al said, many leagues have their own rules. Some say the pitcher is pulled after 2 others vary. Typically (not always), in 10U league play, pitchers are not throwing hard enough to inflict to much serious damage. Although you do not want to hurt other players and at some point enough is enough, 10U league play is a developemental stage and you do need to let the pitchers work through their adversity. Immediately pulling them just because the hit a player or two is not always the answer.