Circa 2012, and disabled-by-default since Ubuntu 16, but still a system wide toggle instead of a per-use option:
> Ubuntu, a widely used and influential GNU/Linux distribution, has installed surveillance code. When the user searches her own local files for a string using the Ubuntu desktop, Ubuntu sends that string to one of Canonical's servers. (Canonical is the company that develops Ubuntu.)
> [..] Ubuntu uses the information about searches to show the user ads to buy various things from Amazon.
> Ubuntu, a widely used and influential GNU/Linux distribution, has installed surveillance code. When the user searches her own local files for a string using the Ubuntu desktop, Ubuntu sends that string to one of Canonical's servers. (Canonical is the company that develops Ubuntu.)
> [..] Ubuntu uses the information about searches to show the user ads to buy various things from Amazon.
https://www.fsf.org/blogs/rms/ubuntu-spyware-what-to-do
https://www.gnu.org/philosophy/ubuntu-spyware.en.html