Just to offer a slightly different perspective, I'm a expat living just south of the US.
Many babies have their ears pierced here - close friends of mine just had their baby girl's ears done when she was 6 months and in every single picture she's smiling. Numbing cream was used, she didn't feel a thing and hasn't had any issues with healing.
Neither of her parents are "chavvy", both are highly educated professionals who are fantastic parents. I suspect part of the reason it is as accepted in the US and South America, as a norm, is that it isn't attached to class. In the UK, as evidenced by the comments above, piercing a baby girl's ears is "chavvy", looks "common" and "cheap" - there doesn't seem to be that same attitude here.
I don't really have an opinion on it (and have boys so don't have to worry about it!) In the UK, a baby girl with pierced ears elicits a certain reaction as it's so closely linked with a social class.
Over here, a baby with pierced ears has no bearing on class whatsoever and therefore nobody gives it much thought. And from that point of view, I can see where PrincessBabyCat is coming from given that she is American. It's not such a big deal there.