Scott Trezza is frustrated with Spotlight in Yosemite:
Spotlight searches on my MacBook Pro running Yosemite always reveal files on other users’ accounts. If I put the other users’ home directory into the Privacy section of Spotlight in System Preferences, then those same users are unable to enjoy the convenience of smart mailboxes in Mail and other conveniences of Spotlight when they are on their own accounts. Is there a way to tweak Spotlight from revealing the contents of other user accounts?
I looked for documentation or other complaints about this issue, and was unable to find any. I tested whether I could replicate this on my own system, as I don’t routinely work on computers that I share with others.
Read more here:: Mac 911: Does Spotlight reveal other users' files?