As ESET's BYOD Infographic shows, BYOD is no LOL matter, bringing with it some serious risks to company networks and data. Based on an ESET Harris Interactive survey.
Another BYOD risk factor is the practice of letting someone else use the device. This could be "just" a family member or friend but it introduces the possibility of that person gaining access to the company network or sensitive company data stored on the device.
===> Furthermore, if this "other person" is not trained in safe computing practices there is a serious risk of them getting the device infected or compromised. <===