Everybody remembers when Ubuntu added online sources for the search functionality and users were not happy with the decision. It looks like Apple now had the same idea with Mac OS X Yosemite and Spotlight will do a similar type of search.
The option to search in other sources than the local ones was implemented in Ubuntu 12.04, which was released back in April 2012. As omgubuntu points out, Apple is looking to do the same thing with Spotlight, but the Mac OS X users don't actually know what feature they are receiving.
It looked like a great idea when Ubuntu first made this modification for Unity, but users slowly became annoyed with it. What if one doesn't want to search in online sources? In Ubuntu, users can open the search field with a shortcut that only lets them look in the local files, but very few power users actually make use of that.
Canonical refined the search feature in time and added scopes, allowing users to choose what online source actually interests them. The Amazon search, which was the one that got people riled up, can be disabled with one click and Ubuntu can be turned into an offline machine immediately.
The problem with online searches is that one doesn't really know what happens with their data. Ubuntu had the same problem. Users found out that Amazon was able to tell what they were searching for and the company would have been able go back to the IP and match the search term. Canonical eventually fixed this by making sure that all searches went through one of their servers.
Some users felt that the problem was only moved by one step. The searches were still going to a third-party company. In any case, the online search in Ubuntu has been accepted by the community to some degree, and some users disable it from the start.
Now, what happens with the searches in Spotlight? Maybe Apple is making the same mistake, and who knows where those particular search terms end up. It's difficult to say whether Apple took “inspiration” from Ubuntu with this feature, although they have been suspected in the past of lifting the Ubuntu Software Center concept, for example.
It's very likely that the Cupertino giant knows all there is to know about Canonical and its work, but Spotlight is very different from Unity in many respects. It will be fun to see whether Mac OS X users try to find out where the searches go and what happens with them.