My DS was born with a load of dark hair and never lost it. When he was younger he had really bad eczema and was constantly covered in cream and ointment. This always got in his hair and made it all greasy. So we used to wash his hair every day when he had a bath.
However, now he is a bit older and his eczema is much better and so he is not such a greasy little thing all the time! Also he is no longer in his baby bath and so it is more difficult to wash his hair as he cant lean back as well and those cap things you can put on are crap.
The last time I washed his hair was a couple of weeks ago when I olive oiled his cradle cap. However, since then his hair just doesnt seem that dirty or greasy and I am thinking that it would actually probably be better for his scalp if I left it as long as possible between hair washed. He still has a bath every day with Oilatum as part of his bedtime routine.
What does everyone else do - how often do you wash your DC's hair?