Photograph by Aaron Suozzi/Corbis
Backyard zip lines -- cables suspended in mid-air for people to slide across -- have become increasingly popular and can be purchased for as little as $150. These are not the zip lines you find at resorts, but smaller ones that typically run from 100 feet to 400 feet. Injuries from one can be life-threatening if it has been strung high enough from the ground. As with tree houses, insurers look askance at zip lines because of the risk that someone will be injured; they want you to disclose if you have one and may then exclude it from your policy.