Most people believe that when they use one of the popular search engines (e.g., Bing, Google, Yahoo, DuckDuckGo), that they have effectively searched the entire Internet. That belief is erroneous for a couple reasons.
CNN Money has a good report about the Shodan search engine, which was developed specifically to search what I call the nooks and crannies of the Internet. Shodan users can find devices connected to the Internet that other search engines don't necessarily focus upon:
"... servers, webcams, printers, routers and all the other stuff that is connected to and makes up the Internet... traffic lights, security cameras, home automation devices and heating systems... control systems for a water park, a gas station, a hotel wine cooler and a crematorium... command and control systems for nuclear power plants and a particle-accelerating cyclotron..."
If it isn't obvious to you, these search results have huge privacy and identity theft implications for a variety of reasons. Many users connect devices to the Internet which they shouldn't connect. Or don't properly secure their Internet-connected devices with firewall software. You can bet that since the good guys already know about and use Shodan, then the bad guys will, too, and hack into unprotected devices, steal identity information, and/or cause havoc.
The second reason: many consumers are trapped in the search Filter Bubble, and don't know it.