Well, I started letting my oldest stay alone for 30-45 minutes while I ran to the store or went for a walk- stuff that kept me close to home when she was 5. She's almost 8 now & I will allow her to stay alone if she's sick (just feeling crummy, not on the verge of dying!) & missing school. I am very flexible in my work & am close to home too- usually only gone 3-4 hours max. She calls me on the cell phone if she has a need or a question. I call her frequently to check in, too. We have gone over & over issues w/ the door, the phone, friends, etc. & she is to stay in the house at all times. NEVER answer the door & only the phone, if & only if she sees my # on the caller ID. I will also let her watch her 4 year old sister for 30 minutes or so, if I have to go teach a class or drop something off quickly very close to home, esp. if dad's on his way home.
I KNOW SOME OF YOUR HEADS ARE EXPLODING AT THIS MOMENT... but I know & trust my kiddo very much. My kids are not prone to pyromania, extreme mess making or other acts of risk taking. Together & alone, they usually just hang out & watch TV & get a snack. We are in contact when apart, and my oldest, for all her quirks, has always shown herself to be a responsible child, very mature for her age.
My mom left me alone for a number of hours regularly from the time I was 5 on. A classic latch key kid. We were in a mobile home park too, in a very rural part of Azle. Much riskier than my current neighborhood! I can't say I particularly enjoyed it, but I also became very self-sufficient & responsible. We can do our best to protect our kids- & we should, but they also need to have opportunities to develop their own strength. To become more responsible, to develop your trust & learn a bit of self-sufficiency, too. Now, often when I call to check in on my oldest, she'll say, "I'm fine. Everything is fine. Bye!" She is learning these important life lessons in a safer environment that I did, & I'm usually no more than 15-20 minutes away, and always in cell phone contact. I can't say most of us old latch-keyers had such a safety nets- I know I didn't. I was on & off the bus by myself everyday. I take my kids to & pick them up from school everyday. The BUS! Now that's an environment I don't feeel my kids are safe in!
As several of you have noted, it DOES depend on the child. I know 16 year old that shouldn't be left alone for a moment & 7 year olds are more mature & responsible than many teens. And if we never leave them alone...even as teenagers??? how in the world are they going to become competent adults w/o out us there "heliocoptering" or hawking them?
I HIGHLY recommend the DVD & CD sold at http://www.thesafeside.com/ They are wonderful resources to start a dialogue with your kids about all sorts of stuff related to strangers & even teachers, coaches, door safety, phone, etc.
Just my thoughts... D.