Yep...but we also know better, now, too. I seem to always have a "story" to center my caution against. Remember that story of the little English girl taken from her hotel room while she was sleeping and the parents were down in the restaurant? Ick. I don't think I would leave a 9 & 7 year old alone, even if they were in a familiar place like home (the 9 year old might be ok, but not really fair to have them responsible for the younger sib). That's just not ok, IMO.
