I do that all the time because I live my life dangerously, plus is the most common practice among users, so I also do it to test user experience. I can count the fingers on one hand for how many times I corrupted my database in 6 years. The hub must lose power at the wrong time for the database to get locked up. But when it does, you will know it and the Soft Rest is there to get your hub back online. Now, to avoid the hub eclipse, it is recommended to always shut down before unplugging.
No it is not common. However, the symptom can have many different root causes. Network issues are the most common. In rare situations a hardware malfunction could be the problem. As rule of thumb, if Diagnostic Tool isn't available, then troubleshooting network issues would be first step, and if that doesn't resolve, the warranty case would be next to make sure you aren't dealing with a hardware issue. If Diagnostic Tool is available, then Soft Reset is the first troubleshooting step.
