About 10 years ago, "semantic web" was popular in scientific community.
Some of that technology did find its way into major search and related products and services,
from Google to Microsoft.
Now, with NoSQL movement and some attention on Graph databases,
RDF (a language of Semantic Web) is finding new usage.
By the way, similar is happened with SVG, that took good 10 years
to start getting some real usage...
podcast: @IEEE Software Engineering Radio