The use of PKI and digital certificates has become an integral part of how the Internet works today. The range of devices that use digital certificates includes WiFi routers, mobile devices and many others. As the use of certificates expands, so too do the challenges for managing the keys associated with them and possibly revoking or replacing them in the event of a compromise or event such as Heartbleed. One of the problems that has faced CAs and their customers in recent years is the rash of mis-issued or stolen certificates that have been used in attacks and malware campaigns.
Source: https://threatpost.com/expanding-use-of-pki-in-variety-of-devices-holds-challenges/109251/