An article by Consumer Reports highlighted the dangers of retractable leads:
Heather Todd didn’t bring a leash with her the day she took her pooch Penny to a pond near Boston in 2005. So she borrowed a retractable dog leash to help keep her Labrador retriever in check. But it didn’t. The 90-pound dog suddenly took off running and dragged Todd across the sand.
When she came to a stop and recovered her wits, she spotted something lying on the sand. With horror, she realized it was a human index finger; with greater horror, she realized it was her own. The cord of the retractable leash had looped around her finger and pulled taut when Penny bolted.
“It just cut it off like a sharp knife,” Todd says.
The article went on to describe how retractable leashes can be dangerous to your dog as well as to you, and quoted a professional dog owner who recommends using a solid leash no longer than six feet long.