My state recommends 11 as a guideline. I was thinking 9 or 10 for short runs up to the store.
I think that we've become really overprotective as a society and it is now nearly impossible to discern right and wrong out of the things our parents hardly gave a thought to. My mother nearly flipped her wig the other day when I let my 7 year old cross the street herself and I recall crossing my street in Kindergarten. She is certain that she would have never had allowd that. LOL!