>it's mainly been girls that have provided rebukes based on gender. Not sure where 2 and 3 year old girls are getting it from but the most often gender-biased comments I've heard targeted at the boys has been "pink is only for girls" and "that's not for you it's for a girl". Strangely in my limited experience (though I work with young children every day) I've yet to hear any boys do the same sort of thing.

This does not surprise me in the least. Females tend to be more socially orientated than males - so any cultural memes are expressed through them more strongly.