In this age of unbreakable software and super-reliable hardware, human error is responsible for the vast majority of unplanned outages.
Sadly, the problem is getting worse, and we see an alarming increase in willful deception, "fake Oracle experts", whose goal is to fleece the unsuspecting IT shop.
The fly-by-night "poser experts" carefully hide their resumes and verifiable work history, others resort to outright deception, like scumbags who create fictional Oracle experts, complete with a photograph and convincing credentials!
The problem of inexperience and human error has several root causes. On one hand we see desperate job candidates who "puff" their job experience, often claiming that their unpaid years of dabbling with Oracle on a PC constitutes real experience.
Read more about how bad DBA's destroy databases.