Surveillance Hijacking
Cyber criminals can potentially use your PC or laptop camera to see into your home or office, and even listen in if they can get access to your device's microphone. This breach is not just remote access to visuals and audio – a captured IoT device on your network can passively and actively learn things about the rest of the network using basic Linux networking tools. Given that most IoT devices run Linux, a hacker has a good chance of installing common malware to learn all about you or your company.
This again reinforces the fact that all IoT devices need to be locked down, not just the central control point, such as a router. The security-savvy and technically capable should do regular security sweeps to check for unusual behavior, but unfortunately, "unusual" can be hard to define. You should also be prepared to reset IoT devices back to their factory settings and to reset the credentials to something more difficult at any time.