Mom of a 16 YO DD here. DD is super responsible. She is very samrt, and has a lot of common sense. she has been coming home alone after school since she was 9 years old. She has been home alone during the summers since she was 11. And no, DH and I do not work close by ( we are each ~45 minutes away).
DH and I are also fairly permissive about her activities and what not. Now that she is driving, while still permissive about her going places, we are very specific about where she is, who she is driving, when she gets places and leaves places she needs to text us etc. (She has had her license 1 month).
DH and I are going on a mini-vaction to vegas in the fall, and we will NOT be leaving DD alone. We are having a college-aged aquaintence of ours not necessarily baby-sitting, but at least keeping an eye on things...and making sure she is awake in the morning. DD isn't happy about that...but OH WELL. I might feel differently if we were only going for a night, and on a weekend, but we are leaving on a Sunday and coming home on Wednesday.