Enjolrass I agree with you, it's not always family friendly in town. I let my dd aged 11 go out in town with her friends and a mobile in the day, but if I am honest, it does worry me. I am not at all convinced there is no 'stranger danger' as she is almost female adult size and as an adult female, I have been flashed at, groped, commented on (numerous times) and asked for money from people for drugs (well, obviously they don't say that but that's why they are agitated and a bit odd and asking for money for hostels/cars without petrol etc), again, numerous times. I have also been followed late at night twice in two different countries and had to run for it (including one taking refuge somewhere).
I am not concerned about the 'big stuff' of being abducted by a stranger, I get that the danger for sexual abuse is often those close to you, which is why I am not a fan of sleepovers having been approached at a sleepover aged 10 in an inappropriate way.
But, it's not true that strangers won't come up to you, or speak in an unpleasant way or scare you a bit!
I think it's more important to teach growing pre-teens and teens how to deal with this. I've told my children if they are on public transport or in a situation and they start to feel uncomfortable or someone starts acting in a way that seems odd or threatening, don't wait about to find out if they are dodgy, just move. Get off the train and get on the next carriage. Get out of the queue you are in and come back later. Completely trust your instincts on this one. The biggest risk for me is that I have two very compliant and polite girls who will just sit there if something nasty unfolds.
I really don't agree there are no risks and it is all in parents heads, but the answer isn't to never let your children out til they are really old.