Where I live, the current by-law states a leash no longer than 6 ft can be used for walking your dog. I'm pretty sure that's the common law in most areas - how much it is enforced is another story.
I've been hurt (massive hand burn/cut) from a retractable leash. We only use it now when it's on the beach or deserted walking trails where I know we will run into very few other individuals and dogs. I'm generally not a fan of those who use them to walk their dog everyday - sorry.