Mac: In order for Spotlight to work properly, it needs to send your search data to Google, Apple and Bing. Initially, it seems easy enough to disable this if you care about privacy, but as users over on Hacker News note, it's not as obvious as it seems.
When you're using your Mac with all the default settings, anything you search for in Safari or Spotlight gets sent to Apple along with whatever search engine it's pinging. It's not totally clear why your data needs to go to Apple, but that certainly makes searching with a search engine like DuckDuckGo slightly pointless. To turn all this stuff off and get a bit of privacy back you'll need to disable two settings:
- Disable Spotlight Suggestions and Bing Web Searches. Head to System Preferences > Spotlight > Search Results and uncheck those two boxes.
- Disable Safari's Spotlight Suggestions. Head to Safari > Preferences > Search and uncheck Spotlight Suggestions.
From the look of it, a number of processes in Yosemite are phoning home to Apple, but it's not totally clear why. For now, disabling Spotlight seems to cover the biggest suspected privacy intrusion. Check out logs on GitHub and the threads on Hacker News for more info.