There are two issue:
1) In Mavericks, you could search "When was George Washington born?" in Spotlight and one of the results would be Web Searches. When you clicked on Web Searches result, it would open your default browser and show the search results.
See, for example, here: Use Spotlight in OS X Mavericks to find files and more
Does Yosemite Spotlight do this?
2) If not, do you get any web results?
Previously, I didn't. But when I selected English (US) as my default language (I live in the US), I get Bing Search "ebay.com" when I search for "ebay."
So, on the one hand, they've enhanced Spotlight because when I click on ebay.com in Bing Search, it gets me directly to the site, whereas with Mavericks Spotlight searching "ebay" would just show me search results in Chrome for "ebay."
On the other hand, they've removed the Maverick's web-search functionality. To search for "When was George Washington born?", I have to open a browser to do it.