I have stopped going to the cinema for a reason such as this.
I went to see the last in the LOTR trilogy and there was a women with a young boy of about 4 or 5 in the cinema. The boy was allowed pretty much to do what he liked during the film and his favorite activity turned out to be walking up and down the stairs. This in itself, although a bit distracting, wasn't so bad but when he was a sufficient distance from mummy he liked to TALK to her.
I swallowed it for about an hour and a half and in the end got up from my seat, went over to his mum and asked quietly if she could try and keep him quiet in his seat. Her response was to yell at me something about single parents being allowed to have a night out, then she got up and left.
She was clearly upset, and it made me think that perhaps she had no alternative and was desperate to get out of her house or something, and I felt a bit bad.
I know stopping going to the cinema is a bit of an over reaction but I want to enjoy movies on my terms, so I wait for Blu-Ray now.