If not properly secured, connected cars threaten to expose sensitive consumer information. With data being passed between so many different connected channels, it’s easier than ever for hackers to get their hands on personally identifiable information.
It is very difficult to select a public key or a set of public keys that can be trusted for a long period of time. If the wrong public key is used, a website can be bricked until the server header expires. The wrong key could be provided accidentally or by an attacker. As in many cases, a site can be bricked where the administrator knows nothing about HPKP, or it’s been redirected by an attack.