Big data iceberg
Lots of people thought the semantic web was going to be the next big thing on the Internet, web 3.0 and such.
Google and Facebook invested a lot of energy in it, and then people didn't use it in ways they anticipated.
It's there, but all hidden below the surface. Our search results are more tailored to us, our Facebook News Feed is magically pulled from the sea of possible posts, in a process that is almost entirely opaque.
This is the big data iceberg.