The article on jailbreaking an iPhone overstates the risk, saying the iPhone could lose all value, when it will only possibly lose the warranty.
"2. Evaluate the Risks
A recent ruling from the federal government determined that it is not illegal to jailbreak or unlock an iPhone or iPod Touch. However, jailbreaking still involves risks, say the experts. Discuss these with your teen:
- Voided warranty. “Apple could consider it a violation of your terms of service,” warns Scelsi. “You’ll lose support from Apple.” So, if the device is bricked, you or your teen could be out the cost of the iPhone or iPod Touch."
[from "Your Security Resource, Is Your Teen Jailbreaking?," by Kim Boatman, Find Under: Online Family Safety", Sunday, Feb 9, 2014]
If Apple removes the warranty, the iPhone is still is a workable device, and can be factory reset and will then be completely usable. The user / teen would not be "out the cost of the iPhone" and would only lose the warranty.